We hadn’t seen the ghost — or one another — all day Saturday, and I was starting to wonder if we’d see her on Sunday. Julie’s theory was that Sally had exhausted herself the day before dealing with Little Belman, telling me the secret about her identity that she’d kept from everybody except her brother for more than one hundred and fifty years, and remembering all about her parents and her childhood and joining the army and the Battle of Antietam.

“She probably doesn’t have enough psychic energy to show up right now,” Julie said. “I think when the ghosts stay away it can be because they need to recharge their batteries, so to speak.”

“Or that their batteries are just running out and maybe can’t be recharged,” Greg added. “So to speak.”

“Right,” said Julie, who clearly liked it when Greg repeated the way she said things. I rolled my eyes. I didn’t think much of their theories, but I didn’t have anything better to suggest so just kept quiet.

We practiced for a while — all our old standards, plus without our even discussing it we launched into a rock-and-roll version of “The Battle Hymn of the Republic.” I remembered Sally singing it with me — and then soloing — the day before, and wished she was there to sing it with us just then. That would have been cool.

After the last “Glory, glory, hallelujah,” Julie decided we’d practiced enough. She also decided to fill us in on details about the Battle of Fredericksburg that she’d stayed up late the past couple of nights reading about.

“So tomorrow, December 11, is the big day,” she said. “That was the day the Union army engineers finally got the pontoons down to the river, and the army started crossing over into Fredericksburg, but it got very complicated very fast.”

“Like how?” Greg asked.

“For one thing it was just twenty-four degrees out, and they started at three in the morning, so it was freezing and it was hard to see. But at least the river wasn’t frozen solid. The engineers had to anchor dozens of the pontoon boats side to side all the way across the river, which is pretty wide where they were trying to cross, and then build the bridges with planks on top of the pontoons.”

“Wait,” I said. “You said ‘bridges’ plural?”

“Right,” said Julie. “Three pairs of bridges. One to cross at the north end of Fredericksburg, one to cross a mile away at the south end of town, and a third one downriver another mile farther beyond the town. Half of the Union troops, about sixty-five thousand men, would go across the first two bridges into town — they called those the Upper and Middle Crossings — and attack the main Confederate force at the Rebels’ defensive position outside of town in Marye’s Heights. Sally and her brother, Frankie, and the Irish Brigade would have crossed over there and been in that part of the battle.

“The other half of the Union force would cross farther downriver at what they called the Lower Crossing and hopefully surprise the Confederates by sweeping around behind them from the south and east. Only that’s not what ended up happening.”

“Why didn’t it?” Greg asked.

“It was about as ridiculous as them having to wait so long to get the pontoons,” Julie said. “Major General William B. Franklin was in charge of the troops at the Lower Crossing and he messed up his orders from General Burnside. On December 13, Franklin sent only thirty-eight hundred men to attack the Rebel line instead of all sixty-five thousand!”

Greg and I stared at Julie, bewildered.

“Why didn’t he double-check with General Burnside?” Greg asked. “I mean, why would they send that many soldiers down there, but only want him to use a handful?”

“Yeah,” I said. “That doesn’t make sense at all.”

Julie nodded. “I know. I told you it was ridiculous. But all the historians agree that the order General Burnside wrote down at about three o’clock in the morning, just hours before the attack, wasn’t clear. General Franklin thought General Burnside wanted him to hold most of his troops back near the river. Just in case of, well, who knows? Nobody to this day has been able to exactly figure out why Franklin didn’t send a messenger back to Burnside to double-check the order. The whole battle would probably have turned out totally different. So instead of the Union army overwhelming the Confederate defenses, the Confederates were able to push that one lonely Union division of General Franklin’s back to the river without too much trouble. It was at this place we now know as Slaughter Pen Farm.”

“I know where that is,” I said. “We’ve driven past it a million times. It’s a few miles from here.”

“Right,” said Julie. “Well, it turned out there were nearly forty thousand Confederate troops positioned up on high ground overlooking Slaughter Pen Farm, way more than anybody on the Union side thought. Even at that, one Union division still managed to break through the Confederate line — briefly. But then when there were no reinforcements sent in, the Yankees were forced back by the Confederate counterattack. I think there were something like five thousand Union casualties in that part of the battle, including some other smaller fights, and cannon fire back and forth. And four thousand Confederate casualties.”

I could picture now where all that fighting had been at Slaughter Pen Farm, but what I couldn’t picture was nine thousand men there — dead or wounded or injured or captured or missing in action.

But at least it was all starting to make sense — the geography of it, anyway. I knew the Rebel defenses and artillery had been lined up for miles south of Slaughter Pen Farm on what is now called Lee Drive. People drive there all the time to check out the old cannons and Confederate trenches and Robert E. Lee’s lookout post high on what they used to call Telegraph Hill. It’s part of the national park, although most people just ride bikes and jog and rollerblade up and down Lee Drive, not really thinking about what an important Civil War site it is.

“I wonder when we’ll see Sally again,” I said. “It would be good to ask her what she knew about Slaughter Pen Farm and the fighting on Lee Drive.”

“I bet she didn’t know anything about it,” Greg said. “Because she was in town the whole time, and there wasn’t any TV or radio or anything to let people know about what else was going on even just a few miles away. I mean, according to Julie, General Franklin didn’t even ask General Burnside a simple question, like, ‘Are you out of your mind? You just want me to send in one division?’ ”

“I wish Sally was here so we could just ask her,” I said again.

“What happens if she doesn’t show up?” Greg asked quietly. “How will we ever help her find out what happened — how she ended up missing, and how she died? What if she used up all her, what did you call it, Julie? — her psychic energy — telling Anderson everything on Friday, and now she’s just, well, done.”

“I can’t believe that,” I responded. “She was so excited to be remembering everything, as hard as it was to talk about. I had the idea that she felt sort of free, getting to tell somebody that she was really a girl. She didn’t seem all staticky and fading in and out like our other ghosts did when they were nearing the end of their time being able to see us and talk to us and everything.”

“I just hope it’s what I said before,” Julie said.

“You mean recharging her batteries?” Greg asked.

Julie nodded. “I’m not sure how that happens, exactly, except maybe it’s like us taking a nap.”

“Or going to sleep at night,” I added, “which all this week I bet is something none of us have done very much of.”

Greg yawned, as if to prove my point. Julie and I couldn’t help it: we yawned, too. Then we all laughed, not that it was all that funny.

We waited another five minutes, none of us saying anything, all of us hoping. But in the end there was no Sally. Not that day, anyway.