"What's the infinite monkey theorem?" she asks, when it comes up. He's sitting behind her, flipping through the files, too fast to have read them if it was anyone else.

"It's a theory," he tells her, looking up. "A theory that a room full of monkeys with typewriters, if given all the time in the world, would eventually churn out the works of Shakespeare."

"Really?" she asks, leaning across the table.

"It's possible," he says, "But highly unlikely."

"What's 'highly unlikely'?" she asks.

"Well, the odds of a monkey pressing any key is 1 in 26. Including the space bar is 1 in 27. Let's use 'The Adventures of Sherlock Holmes'. The first sentence is, 'To Sherlock Holmes she is always the women.' The odds of him pressing the first right letter is 1 in 27. Multiply that by 1 in 27 for every letter after it. Forty-two times, since there's forty-two characters."

"Well, how much is that?"

"The odds of just the first two words is 1 in 5.559061e+15." He answers almost instantaneously.

"That's a lot. But it's possible?"

"It's possible," he concedes. "But highly unlikely.

About the same odds of you finally noticing I like you.

The next time they're discussing odds, it's in a casino, and she's moved on and has a son. He's been acting weird and jumpy all week, and she doesn't want to scare him by asking him what's wrong.

"What has the best odds?" she asks him, sweeping her arm around to include the entire room.

His eyes jump up and he scans it. "The slot machines," he tells her promptly. "But electronic poker if you play right."

She digs into her pocket and pulls out a quarter. "What're the odds of it landing on tails?" she asks.

"Fifty percent," he tells her, and then goes on. "Actually, a study being done at Stanford is starting to suggest that the percentages are actually 49% chance of landing on heads and 51% chance of landing on tails. Although that could, of course, be coincidence, but it might also have to do with a slight imbalance in the weight of the coin."

"So always call tails?" she teases him.

"Well, those are just a compilation of data. The effects of previous and future tosses have no effect on an individual coin flip, and overall it won't have an effect large enough to notice—" he realizes it was a joke and cuts himself off, blushing.

"So no difference?" she prods him again, trying to get him to talk. Because she doesn't want him thinking about whatever-it-is that's bothering him, and okay, maybe she finds his rambling explanations a bit cute.

"Well, a small one," he concedes. "Won't help you by much." He smiles. "Always better odds than a slot machine."

Better odds than almost anything.

The next time, she isn't teasing him. He's standing on her doorstep in tears.

"Why?" he asks her as soon as she opens the door. "The CIA gives out hundreds of operations every year, and has hundreds of operatives. Why'd she get that one?"

She stands there. She doesn't know what to say.

"CPR done by trained medical professionals works 30% of the time. Why didn't it work on Emily?"

He's openly sobbing now, and she steps outside and hugs him. "Sometimes, it just doesn't work that way." Neither of them speaks for a long time, until he's run out of tears for the time being, and she manages to ignore the guilt at not telling him.

Then he looks at her. "Why are the odds always against us even when they're in our favor?"

I don't know. Odds are we never will.

Much later, when Emily's home and she thinks they're all safe, for once, her phone rings, and their roles are reversed. He holds her awkwardly while she cries, and Morgan talks to the doctor. She's too distraught to make arrangements, and she vaguely remembers nodding when Hotch offers to take Henry for the time being.

What will she say to Henry? She never thought he'd lose his father. He didn't have all the dangers of her job to worry about. She counted on Will being there if something happened to her.

"Why?" she gasps out. "Why couldn't they bring him back?"

Reid answers without thinking. "CPR only works 7% of the time outside a hospital," he tells her, and it doesn't make her feel any better.

"The things you were saying, when Emily…went into hiding?" She asks it later, when the tears are gone and she's making calls she never thought she'd have to make.

"About what?" he asks her, and she realizes he's said a lot of things when he thought that Prentiss was dead.

"About odds, and it not being fair." And she's counting on him remembering, even if his eidetic memory only applies to things he reads.

"Yeah."

"What were the odds of Will being standing right there when the sinkhole…" she breaks off.

And she's pretty sure he's on the verge of calculating the ground Will walks—walked—in a day and all the places he could be and the places most susceptible to sinkholes, but he doesn't.

"It doesn't matter. It's still not fair."

Is it ever?

It's months later, when they're back from a rough case and Rossi dumps a 5000 piece Jigsaw puzzle on the table. "Come on, we've got time." And she wouldn't have expected it of Rossi, but it's probably exactly what they need, sitting down as a group and trying to put a massive picture of the solar system together.

And pretty soon they're all sitting down around it, and Emily's trying to put together the edges and Morgan is trying random pieces that would never fit and Reid is moving five times as fast as the rest of them, because somehow he's seeing the patterns that they're not.

"Not fair!" Emily tells him, but she's laughing. "I was working on that." He guiltily sets down the star Prentiss was working on, completed. "I think we should blindfold him."

"That's not fair!" he objects. "The entire purpose of a Jigsaw puzzle is using sight."

"The purpose," Emily tells him, "Is making you feel stupid."

"Isn't that what Reid's doing?" Hotch asks innocently, and they're laughing again.

"No," she puts in. "The purpose is making you feel stupid and then not stupid when you finish it. Reid never makes us feel not stupid." But she puts an arm around him, to let him know she doesn't mean it.

"JJ's right," Prentiss is pleased to have a supporter. "We seriously need to blindfold him."

"He needs his own puzzle," Morgan puts in. Reid sticks his tongue out at Morgan and finishes Jupiter.

"You could all just work faster," he says innocently.

"You could go sit under the table," Emily shoots back. "Venus is mine. Nobody else can help with Venus."

Reid doesn't have a response, but he gets her back, admittedly about two hours later when she's finally put Venus together except for one piece. They still have hundreds, if not thousands, left, and she's been sorting through them for at least half an hour to no avail.

"Sure you don't want help?" he teases her back.

"Yes." Ten minutes later. "No. If you're so smart, you find it."

"It's behind your ear," he tells her. Her hand goes back immediately and she finds it.

"Oh!" Prentiss snapped it into place, looking a bit too pleased with the magic trick to be mad.

"What are the odds we finish this tonight?" Emily asks, as the day winds down and they still don't have a case.

"Depends," Morgan puts in. "On how late we stay."

"On how much caffeine Reid consumes," she puts in, happy for the first time in a long time.

This time, the odds are good either way.

And months later, his birthday rolls around, and he's clearly uncomfortable with all the attention. But he's still way too happy for having gotten another year older. She always figured it didn't bother guys as much, but he's acting like it's something undeniably good.

"Why're you so happy?" she asks him later, handing him a slice of cake with a fork stuck in it. He takes it, and grins. "The odds are going down."

"What?" Because sometimes she feels like he's speaking another language.

"Of schizophrenia. The odds of it developing are much smaller," he tells her.

"Odds are in our favor now, yeah?" She asks him, and he blinks before he remembers their conversation from what seems lifetimes ago, standing in the hospital room in a state of shock.

"Yeah." He starts eating the cake, and they stand there for a while.

"I should get the others," she said suddenly. "We haven't sung yet."

"Please don't," he begged.

She let it slide. "Fine, but don't think there won't be singing."

He ignores her and finishes the cake, tossing the paper plate and disposable fork in the trash. Then he leans against the counter, and he stares off into space while she stares at him.

The odds are getting better every time.

The last time they talk about it, he's scribbling some sort of equation on the glass wall with one of Rossi's markers. The case is over, they're packing up to go home, and the only person who would care is Rossi, who already left. Hopefully Reid will remember to erase it and he'll never know.

"What's that for?" she asks, because she's waiting for her laptop to stop updating and shut down so she can get home to her son.

"I'm trying to calculate the odds of forty-three rolls of two dice. One dice is weighted, and the other is completely blank. How many option are there?"

"One," she puts in, confused because the answer is obvious.

"Depends on how weighted the dice is. Sometimes they don't roll all the way. So I'm trying to calculate all the possible permutations given specific weights."

And wasn't that just like him, to make something endlessly complicated for the heck of it. "Why're you using Rossi's marker?"

He looks at it. "Oh," he shrugs. "Didn't notice."

"What are the odds?"

He caps the marker and taps it on the wall with the half-finished equation. "I'm not done yet."

Suddenly, she feels much bolder. "Could you calculate the odds of someone understanding something?"

He thinks about it. "To a rough estimate, if I had their track record and learning curve."

"Okay," she reaches up and kisses him. "What are your odds of understanding what that meant?"

He stares at her, shocked. "Spence?" she asks, after a minute.

"…very good," he tells her, smiling a little.

And suddenly odds don't matter anymore.