By some counts, the Atlantic Ocean contains 85,000,000 cubic miles of water. Within that water are at least 17,500 different species of animals, with each of those species containing countless members.

Bangor did not know these numbers precisely, but he knew his home was large, and that there were many, many fish and other fauna in it (though usually slightly fewer than average in the cubic miles closest to Uncle York).

In short, Bangor knew he could not have been the only living soul in the Atlantic Ocean.

But it sure was starting to feel that way.

The sun had only just set when Bangor swam, alone, into Perkins Cove. There should have been at least some small amount of boat traffic, some deep-sea fishing boat making a late return from a day spent out beyond the continental shelf. But in the hour since Bangor’s arrival, no one had come in or out. It was like the entire town of Ogunquit had found something fascinating and important to do on land. Something so important that they’d forgotten all about the amazing big blue biome they’d balanced their lives on the edge of, and the friends they had swimming out there, to boot.

And yet Bangor couldn’t shake the odd feeling that the humans he was looking for were somewhere close by—around, but just out of sight.

Well, you could be awfully close to someone and still feel very far away. After the past few days, Bangor knew that better than anyone. In the wake of his big blow-out fight with his mother on Friday, he’d been trying to give the pod a healthy distance while making sure he wasn’t so distant that Kittery thought he was trying to escape again.

This was a tough balance to strike.

Bangor knew he should have apologized to his mother and told her how much she meant to him. York, who had many years’ worth of wisdom under his melon, surely would have called it a great personal victory for Bangor if he did so. But Bangor, who possessed far fewer years and a lot more frustration, couldn’t help but feel that rolling over like that would be some sort of defeat. Anyway, Kittery didn’t seem interested in hearing much of anything from him right now—just keeping a watchful eye on him. So he stuck around reluctantly, making sure he was seen but not heard.

If this was a tense situation for Bangor and Kittery, poor Bristol seemed to be suffering from it even more. After just a couple days of silence, Bristol burst out in a frenzy of clicking and tail thrashing.

Why can’t you two just make up?! If you keep being this quiet, I’m going to run away myself!

Which was, of course, exactly the wrong thing to say to Kittery. She’d become upset, and the pod’s already-shaky peace had fallen apart faster than a ship hitting an iceberg. This was when Kittery absolutely forbade anyone from even going near Perkins Cove.

This was also, of course, exactly when Bangor had set off for Perkins Cove.

So now he’d arrived, and even though there was no one to play with and nothing really to do, lingering here still felt easier than going back out to Bibb Rock.

It was actually kind of nice. The boats rocked gently back and forth on waves pulled by the bright moon above. It had been a long time since Bangor had experienced this kind of total peace. It was, in its own small way, an adventure.

Was this, in fact, what it meant to have adventures? To ultimately end up alone? Was there no way to strike out on your own without losing the love and guidance of your family? Was Bangor destined to spend his nights with only the company of the moonlight and the tiny baby mackerel flitting under the dock?

Surely not, right? After all, the first big adventure he’d ever taken had introduced him to his best friend, Lars.

But now, not even Lars was in sight—Lars, who sometimes trotted to the beach on his own when all the humans were off doing whatever boring things they chose to do five days a week. Even the harbormaster’s house appeared to be empty, its lights off for the night.

This last part made Bangor a little nervous. He had watched the comings and goings of Perkins Cove long enough to know the harbormaster was responsible for monitoring who came in or out, raising and lowering the drawbridge whenever it was called for, and giving everyone plenty of warning that a boat was on the move.

But there was no sense worrying about it. In addition to echolocation, Bangor had the gift of excellent night vision, all the better for seeing under dark and murky water. He’d notice anything coming toward him. As long as it didn’t sneak up from behind him. Which, given how little space the small cove allowed for sneaky maneuvering, should be impossible—

Something rammed into Bangor from behind.

Bangor squealed in fright.

So did the thing that had run into him.

Whirling around, Bangor saw Marina, eyes wide, scrabbling backward through the water by frantically wiggling and splashing her webbed paws. Clearly she had seen Bangor floating alone in the moonlight and decided to surprise him as a fun prank—except she’d done too good a job of surprising him.

(Porpoises, it is worth mentioning, do not have excellent senses of smell.)

After a moment’s confusion, though, both animals realized their mistake—and Bangor began to laugh. Porpoise laughter, which consists of a quick short shock of pulses that melt into a happy whistle, is one of nature’s most remarkable sounds. Within seconds of hearing it, Marina had thrown back her head and began to release a chuckling noise that was, Bangor was willing to bet, the otter equivalent of laughter.

After that, it was game on.

With the entire empty cove at their disposal, Bangor and Marina were able to whip and whizz through the water fearlessly, dodging between boats and breakers. Whenever Marina surfaced, starlight danced in the drops that slid down her whiskers.

If adventuring meant leaving his family, Bangor thought, then maybe he’d just have to buck up and do it. He’d done it before, after all, back on that first fateful, stormy night. That had been an accident, sure, but look what it had brought him: unforgettable friends like Lars, Natalie, and now, Marina. If his family didn’t like it, well, they didn’t have to follow him around all the time, hassling him and calling after him!

Bangor!

Right, just like that.

Bangor, over here!

Wait. That was actually happening. Someone was clicking to get his attention.

Bangor froze, and Marina shot past him, nearly slamming into the Grundy family boat, the Kelly Natasha. After she had stopped herself, Marina turned and followed Bangor’s gaze to see who had joined them.

There, joyfully racing toward them, was …

Bristol?! Bangor squeaked in shock. What are you doing here?! Mom told you not to come here! She’s going to blow her top! More than usual!

For a moment, Bristol slowed down, her whistle descending in pitch. Yeah, I know. It makes me sad. Then she brightened up again and swam circles around her older brother. But I’m tired of being sad! I miss you! Let’s run away! I don’t care if it means never seeing them again—I want to be like you!

At first, this made Bangor’s heart pound with joy. Hearing that his little sister loved him so much that she’d follow him to the ends of the ocean … it was every big brother’s dream.

At the same time, though …

Let’s run away!

It was exactly the sentiment Bangor had been thinking to himself only moments ago. But now, hearing Bristol express it, swearing she never needed to see her family again, it sounded … childish.

Of course, his family didn’t just follow him around. They supported him. They brought him joy. Look how much joy he’d felt just from seeing Bristol’s smiling snout right now, for instance.

Suddenly with a clarity as silver and pure as the moon on the water, Bangor understood that he had to set things right with his mother.

Which probably started with him and his little sister returning to the pod.

Bristol, I—

But Bangor didn’t get very far as the world exploded in bubbles and squeaking. Marina had been looking curiously back and forth as the two porpoises argued in a language she could not understand, and now she had chosen to make it clear that there had been entirely too much clicking around here and not nearly enough playing.

Bristol seemed to agree, instantly whistling with excitement and executing a barrel roll as Marina blazed past her. As the otter curved tightly to make her return and Bristol spun around to face her, Bangor realized that his sister and Marina had never really gotten the chance to play together one-on-one. And Marina was quick to catch on to the advantages of having such a small playmate. Just when it seemed she was about to rocket straight into Bristol’s snout, Marina suddenly shot upward and out of the water, where she flew, tip to tail, lengthwise over Bristol’s entire body, splashing back into the water behind the young porpoise as Bristol laughed in amazement.

Okay, Bangor thought, laughing as well despite himself. Maybe going home can wait just a bit.

Then Marina darted off behind a boat, and Bristol shot forward to find her, followed bemusedly by Bangor.

The trio played together like this for the next several minutes. If anyone had been around to see it, they would have been amazed at the sight of the two porpoises and the otter rejoicing under the starry night sky, communicating with one another in a way that went deeper than any language. Bangor never wanted it to end.

But he knew that it had to eventually. And he especially knew it when, after taking a quick break to huff and puff and catch her breath, Bristol raced out in the direction of the drawbridge. She looked out at the wide dark ocean beyond, where shadows and light moved like an invitation, and then turned back to her older brother to ask, Can we do this every day when we’ve run away together?

Okay. That was his cue.

Bristol, Bangor said, drifting gently toward his sister. We can’t run away together. We—

And then he realized: One of those shadows out there wasn’t just a shadow.

It wasn’t a big boat; not a fisherman’s boat like The Marina, or a modified yacht like the Searchin’ Urchin. It was a motorboat, small enough to pass beneath the drawbridge with no problem. And it didn’t have any pingers on, indicating that it wasn’t from around here—just some tourists, probably out for a late-night pleasure cruise. It was possible they didn’t know which cove they were pulling into, or even which town.

That wasn’t the only thing they didn’t know. Porpoises may have had excellent night vision, but humans … not so much. Bangor had watched enough boats bump clumsily into docks after sunset to know that human vision got way worse out on the water at night. To them, the gray flash of a porpoise flank in the dark might as well have been just another line of moonlight on the water.

Bangor, though, could see it all too perfectly as the boat bore down on his baby sister.

It wasn’t a big boat.

But Bristol wasn’t a big porpoise.

And because she was looking straight at her older brother, she had no clue what was coming for her. If she turned now, the boat would only confuse her echolocation. This was it. This was what Kittery had warned her children about. Her worst nightmare. Bangor’s worst nightmare: A boat was going to hit his little sister. Nothing short of a miracle could stop it.

Bangor would just have to be a miracle.

He raced forward, faster than he’d ever known he could. He experienced the following things in rapid succession:

A squeak of surprise from Bristol.

A cry of confusion from the humans in the boat as they finally saw something moving in the black waves below.

A thud as Bangor smashed into his sister, sending her reeling through the water, out of the path of the boat.

A red dull bloom of pain in Bangor’s mind, and the sluggish, confused thought: Hitting Bristol shouldn’t have hurt that much, right? She’s not that big. So why does it feel like I … just … hit … something much bigger …

It was funny. Hypothetically this was the most pain Bangor had ever felt in his life. But as he drifted through the water in a daze, he found so many other things to focus on instead:

The cold, smooth surface of the rocky shore as he washed up against it and stayed there, suddenly too tired to swim.

The roar of the boat’s motor as it peeled out of the cove, headed who knew where—just anywhere away from here.

Bristol poking her head out of the water inches from where Bangor was beached on the shore, whistling frantically, Get up! Get up! Bangor, you have to get up!

Bangor tried and failed to say something in response.

I’m going to get Mom! I’m going to get everyone! You just … stay here!

And then Bristol was tearing out of the cove, too, back out into the ocean.

And Bangor was alone.

Well, not quite alone. Marina raced up onto the rocks around him, sniffing and squeaking. She leaned forward, got something on her whiskers, and jerked back as if she’d been shocked by electricity. She cleaned it off and scampered up to Bangor’s melon, chittering and chattering in his ear, but he was as helpless to respond to her as he’d been with his sister.

Well, it was nice to have some company, at least.

Then Marina looked up at the lights of Ogunquit. She twitched her nose as if smelling something familiar.

Then she tore off toward land, disappearing into the night.

Classic Marina, Bangor thought weakly.

Well, no matter. Before, Bangor had felt like the only living soul in the ocean. Now he got to feel like the only living soul on land, too. It was kind of impressive in a delirious sort of way.

With a huff that should have been a laugh, Bangor had the same thought he had just a short while ago:

Where is everyone?