He notices the box on his desk the second he enters the room. His office is full of stuff, but it is his stuff, and he knows everything that belongs. This box does not belong.

It is not his birthday. Or Christmas. Not that he generally receives gifts for either of those anyway. Not at work. His mother always sends a gift, but she sends it to his home. Regardless, it's wrapped in colorful paper with a bow on top, so it appears to be a gift.

He moves behind his desk, shakes the box, and smiles at the muffled rattle.

"I can just see you at eight years old on Christmas morning." She's leaning against his door jam smirking.

He waits, the question unspoken between them.

She nods. "Open it."

He does, and then he laughs. It's a Logos set. Just last week, they finished an investigation into a murder at a Logos tournament.

"You seemed like you were having fun," she says, and her voice is so sweet, with just a hint of teasing. "Even if you did miss vixens."

He smiles. It's been so long since they played their game. When she rearranged the tiles he was working with, and then gave him a flirty smile and told him he missed one, fire had pulsed through him.

Things between them have been good for months. They're working well together, having fun. Like they used to in the beginning.

After the Marlin case, when he was so broken imagining Sara's face on Debbie's body, he wasn't sure he would ever be able to work with her again. He's so glad he was wrong.

They are friends again. He loves working with her best. This case felt like back in the beginning, when he couldn't wait for her to get to work so they could play.

She saunters over to his desk, and watches him open the box and extract the tiles. He sifts them through his fingers, then plucks eight of them from the velvet bag. He steps closer to her, their bodies almost touching, and reaches his arm around her, dropping the tiles in a pile in front of her on the desk. She turns and looks up at him, and he grins.

She purses her lips, trying to hold back a smile, and he raises an eyebrow, issuing a silent challenge.

She spreads the tiles out in front of her, and he can see the gears of her mind working. He loves watching her think. He knows when she sees it. She gives up on holding back the smile, and it spreads across her face. Her best, widest smile. The one that always makes his heart skip a beat.

With one finger, she slides the tiles until they form a single phrase. "Thank you".

"You're welcome," she says softly. And then she hesitates, and he can tell there's something else she wants to say. He waits, giving her time.

"Remember that case Nick was working on last month? The dead woman under the prison bus?"

He nods, shifting gears. This is not where he thought this conversation was going.

"I was in the trace lab, when he and Hodges were trying to figure out the discoloration on the vic's arm. It was a tattoo. Made with carminic acid. From a cochineal."

He nods again. "I saw the report. That was a good catch."

She hesitates again, biting her lip nervously. "I might have mentioned that I read about it in the book you gave me for Christmas last year. I didn't think- I mean, I just assumed…."

He nods, understanding immediately. "You assumed that I give Christmas gifts to the whole team?" he finishes quietly.

"Last year we were barely speaking to each other," she says, her eyes falling from his face to the tiles on his desk. She reaches out and pushes them around nervously. "I figured it was just an obligation. You had to get me something if you were getting everyone else something."

"You've never been an obligation, Sara," he says, his heart tight in his chest.

She looks up at him, and the longing in her eyes leaves him breathless. There is a long, painful silence, and then she looks away and takes a shallow breath. Her eyes return to his, and he sees that the longing is replaced by uncertainty. "I wouldn't have said anything about the book if I had realized."

"It's fine, Sara," he says. "There's no rule that says I can't buy you a present."

He wonders, for just a moment, what other secrets she could keep. They could keep. He has spent five years hiding his feelings for her. Hiding from his feelings for her. What if they hid together?

"Thank you," she says. "I know I've always thanked you for your gifts at the time. But knowing…. Just…thank you."

He nods, thinking of the gifts he's given her over the years. Always something work related, something that could plausibly be explained as a gift from a supervisor to a member of his team. He tries not to think about the gifts he wishes he could give her.

"Hey, Grissom," Greg says from the doorway. "I got a match on those prints. You're going to want to see this."

He tells Greg he will be right there, and then he sweeps the puzzle she has solved back into the bag, hesitating only a moment before pulling ten more tiles from the bag and leaving them in a pile in front of her.

He nods his goodbye and then follows Greg down the hall. When he returns, Sara is gone, but the tiles have been arranged to spell out "my pleasure". And to his delight, another pile of letters waits for him beside his message.

The puzzles become a part of their daily routine. They leave clues about the cases they are working, about authors and poets they have referenced throughout the day, even once a puzzle within a puzzle when she leaves him the answer to the last clue missing from his crossword.

When a rollercoaster car careens off the track at a local amusement park, he leaves her "sabotage". And after they banter about Henry James and The Turn of the Screw, she leaves him "ghost".

They are caught up in the investigation after that. Too busy for games. The case itself is their puzzle, and they solve it piece by piece.

As they are wrapping it up, he finds a new pile waiting for him, and he picks at it for hours until he finds "cite your source". And then he feels the rush of adrenaline, remembering their conversation before Greg swabbed the seatbelt for semen. The release of epinephrine and adrenaline causes a stimulatory effect, enhancing ejaculation, he had told them.

She's flirting with him. Like they used to. Before he can stop himself, he's pulling out the tiles to spell out "mile high club".

He's gone from his office for the next six hours, but when he returns to finish the paperwork, there is a new pile of tiles beside his message. And it takes him only a minute to puzzle it out. "Overrated".

He sits for a long time staring at the tiles when he is supposed to be doing paperwork. Finally he finishes his work, sweeps away the tiles, and pulls out ten more.

It takes her two days to solve it, and his anxiety grows by the hour. The puzzle is a simple one. The only challenge to it is knowing to split it into three small words. He doesn't know if she is struggling with the puzzle, making it harder than it is, or if she has figured it out but can't solve it for him until she settles on an answer.

On Friday, he arrives at work an hour early, but she is already somewhere in the building. Because she was gone when he left for the day, and the puzzle is sitting on his desk, deciphered. "Ride with me".

He should have known her answer will not be a simple yes or no. That would be too easy. But it takes him only a minute to unscramble the tiles. "My pleasure".

When he looks up, she is in the doorway smiling at him.

After work, in the dusky quiet of the early morning, he takes her to his favorite rollercoaster, and she smiles at him as they fasten their buckles.

They are alone in the car, and as it ticks slowly up the track to top of the first hill he cannot hold back the smile. He cannot remember the last time he was this happy. He turns to look at her, and sees his happiness reflected back to him in her smile. For the first time in a long time, he isn't just happy, he's hopeful. He does not know what is happening between them, how they will solve this riddle of a relationship. But she is the smartest person he's ever met. And if anyone can do it, it's her.

He wants, desperately, to kiss her. But he settles for holding her hand. And then suddenly they are cresting the hill, racing down the track. Together.

Less than 48 hours later, she eyes him warily, crouching on the floor of the garage at the far bumper of Sam Braun's limo, and tells him she knows he recommended Nick for the key position. When she releases the tape measure, it retracts loudly, skittering across the floor back to him, and he can't help but imagine her severing the tenuous new beginning between them, sending it skittering back to him as well.

It has been months since he wrote his recommendation. And though he had his reasons at the time – chief among them, Nick's facility with interpersonal relationships and his own disinclination to squander Sara's time with paperwork when she belongs in the field – none of that feels sufficient to offer her as an explanation. He bumbles the conversation terribly.

She told him once that she wanted to make sure that whatever happened – or didn't happen – between them would not affect his recommendation. He was so appalled by the thought of it, he was stunned into silence. Before he could gather his thoughts, she apologized, muttering her frustration about overtalking around him, and walked away. Now, he wonders if she thinks his silence proves his guilt – if she thinks he is punishing her for the crime of loving her both too much and not enough.

He wonders also if she thinks he has made this decision to protect himself against accusations of favoritism should their relationship progress and come to light; if he is sacrificing her career advancement on the altar of his indecision.

It is sickening to contemplate this silent, imagined accusation. More sickening still: his fear that this accusation could have merit.

Later, in his office, his eyes are drawn automatically to the tiles spelling out "my pleasure", and he can't believe it has only been two days since he found her reply to his invitation. He wonders if he can tell her with tiles what he could not with his words.

He lingers over the letters for far too long, finally settling on "you deserve better". He's not sure if he means the position or his explanation, but he knows both are true.

He leaves the tiles in three small piles, reducing the challenge of the puzzle. He wants her to solve this one quickly.

But all week, as they finish one case and then another, she steadfastly avoids him. The tiles never move.

When Catherine tells him that Sara asked to transport the rape kit back to the lab rather than take the victim's statement on their newest case, his selfish sulking morphs into concern for her. This is not like Sara.

He finds her in the hall, watching through a window as the victim works with the forensic artist. He tries to have a conversation with her about vacation days, but she wants nothing to do with the conversation or with him. He leaves her to her work, and he doesn't see her for the rest of the day.

After they wrap the case, he sees Sara leave with Nick and Warrick, and he bites back the jealousy. His eyes go to the three small piles of round white tiles on the corner of his desk, and with a sinking sense of resignation, he sweeps them into their velvet bag and tucks the set into his desk drawer.

Two hours later, she is sitting, body slumped and eyes downcast, while a uniformed police officer tells him that the officer who pulled her over cut her a break and didn't book her, but he still had to notify her supervisor.

He crosses the room slowly and sits beside her, painfully aware that he is the last person in the world she wants to see right now. He reaches over and curls his hand around hers, careful to keep any hint of censure or judgment from his voice as he offers to drive her home.

She doesn't respond immediately, and they are frozen for a moment like that, side by side, hand in hand. Just waiting.