“Get up!” I pulled at Jack’s good arm.

I knew we had a very small window of escape. Brigid had been momentarily disabled. She was in some kind of catatonic state, writhing with fury. Twisting like a snake, she mouthed a single word: “Ragnarök. Ragnarök. Ragnarök.” Whether she was weakened by the blood itself or the mere burst of a vital red into her icy world, the moment she recovered, there would be hell to pay.

Jack struggled to his feet, holding his injured hand. A crimson patch of blood soaked the front of his blue tunic.

“Kat,” he said, “are you OK?” Shock and hurt trebled his voice. He opened his palm, and I saw something small glint there before it slipped away onto the blood-soaked snow.

I looked into his eyes and almost collapsed in relief. Jack was back. My Jack was back. I’d just hacked his hand open like some kind of crazed slasher, yet he was asking if I was all right. God, I loved this guy.

“I’m fine. You’ll be fine,” I said, my voice rolling through waves of both joy and panic, “but we have to get out of here.”

Jack’s first few steps were faltering. His legs gave out, and he stumbled to his knees. He was now feeling the exhaustion of the frenetic pace at which Brigid had worked him. Surely the pain of a gashing wound was no help.

A boom, a distant rumble of thunder, bowled over the winds. Though I suspected that the flash of lightning had been a release of Jack’s pent-up emotions, he seemed too weak to produce this reverberation. Whatever it was, I intended to outrun it, a flight over fight instinct kicking in.

I practically dragged Jack across the path and into the woods. When Poro bounded up to meet us, I cried tears of gratitude. As if genuflecting, Poro lowered his swayed back, and I assisted Jack and then scrambled aboard. Poro, the massive beast that he was, ran agilely through the wooded and snowy path. He hurdled fallen trees and scrambled up rocky, snow-covered inclines. All the while, Jack slumped over my back and I could hear him grunting in pain.

About halfway through the forest, I again heard a loud rumble. Was it the groan of timbers? A shifting of the ice field? It was all I could manage to ride Poro and account for Jack behind me. Whatever their source, the cannonade splintering through the forest canopy was just one more thing to escape.

The trees thinned out, and we charged onto the snowy tundra leading to the massive tree, my arrival point and — God willing — our escape hatch. What I saw, though, left me more distraught than relieved. What had once been a seascape of frigid, turgid waters was now rock-solid ice, an endless panorama of immovable stone. Hell had definitely frozen over. But this wasn’t the worst of it. Arriving en masse over this newly formed passageway were dark shadows: hulking, shambling figures as tall as trees. The Jötunn, Frost Giants. Their towering forms charged across the ice, growing closer to the shore with every thundering boom of their march.

From behind us, I heard the careening screech of a sleigh. Brigid, seemingly fully recovered, lashed the dogs without mercy and skidded to a sideways, snow-throwing stop only a few feet from us. Her face was contorted with apoplexy, and her eyes sparked with rage.

So not good.

“You think you can outrun me?” Her shrill scream cracked through the air like her whip.

I flung myself from Poro’s back. Jack, mustering strength, did the same. We pounded the short distance that still separated us from the tree.

I could see that the first line of the hideous Frost Giants had reached the shore. From behind us, Brigid roared to them, “Snjoflóð, release the snjoflóð! Begin the reign of Ragnarök!”

Just as we reached the tree, I heard an explosion and I was slammed, headfirst, against its hollow opening. It was the kind of quake that shifted tectonic plates, the kind of jolt that accompanied a sonic boom.

My head dizzy with pain, I pushed Jack ahead of me into the cavity of that massive tree. If nothing else, it would at least temporarily shelter us from the avalanche I feared had been set in motion. My vision twisted before me, and I struggled to hold on to consciousness. I funneled my fragmenting thoughts as best I could. One snowflake on Niflheim was equal to one hundred million on earth. If the wedge kept the power place open, there was no stopping this cataclysm. Our only hope, Midgard’s only hope, lay in sealing the portal — hopefully, with us on the right side of it. Hopefully. Though I couldn’t help but think that our chances were also in that one-hundred-million-to-one range.

Jack, still stanching the blood flowing from his hand, crouched on his knees amid the snowy shelter of the tree’s cavity. I scrambled over to him.

“Jack, we have to stop the avalanche. We have to destroy this tree. Can you summon the winds to topple it? Or lightning to strike it?” He looked at me with a haggard, yet rallying, expression. “You can do it,” I said, seizing him by the shoulders. “I know you can do it.”

He tried to stand, but stumbled. I got under his arm to support him and felt a charge of current buzz up my arms. With the surge, Jack came to a full stand. I knew that I had to believe, that we both had to believe, we were equal to the avalanche, the Frost Giants, and even the Snow Queen. “We can do this,” I shouted. “A team, remember?”

Then, Jack, his face purpling with pain, released a bellow of visceral origin. His entire body spasmed as if being yanked upward by some invisible chain. My head spun with a building pressure. I closed my eyes and called on my ancient powers and to all the magical forces of the universe, casting wishes across the realms and back through time itself.

The pain became unbearable, an internal siren of screams. My fingers, still grasping Jack, contorted in crippling agony. The roar of the advancing avalanche drowned out everything. Just when I wasn’t sure we could hold on any longer, we were slammed down hard and everything went dark and dead quiet.

I had the vague sensation of wings encircling me from behind, grasping me under my arms, and then Jack and I were gliding effortlessly downward. I felt we were safe until a sudden tug wrested Jack from my hold and there was nothing but emptiness where he had been.