This story is slightly AU, although it generally follows the course of the show. Mild spoilers through mid-Season 2. In this universe, Chuck doesn't know that Sarah's a CIA agent.

--

Sarah Walker wasn't sure how she hadn't heard the rain. As soon as she locked the door of the dojo behind her she felt it all around her. The Orange Orange two doors down was deserted; no one wanted to eat frozen yogurt in the rain. Sarah stood under the awning and gazed across the parking lot, her thumb tucked under the strap of the duffel slung over her shoulder. To the Buy More.

She squared her shoulders and put the face on, pulled her hood up over her blonde hair, and set off at a brisk run across the parking lot, her tennis shoes splashing in the puddles. She frowned at the sudden dampness at her ankles, and was even more irritated when she heard a call from the Orange Orange.

"Hey!"

Sarah slowed her pace, splashing her calves one last time, before she turned to see John Casey hanging from the front door of the yogurt shop. He beckoned her with two fingers, and she shot him a glare. He knew better than to address her directly in plain view. She made an impatient gesture and he went back inside.

She was just yanking open the back door to Castle when she realized Casey's face had been grim.

The air was always cool in the NSA basement lair, and the wet fabric of her workout pants clung to her calves as Sarah took the stairs, still hyperactively aware that she was in somewhat enemy territory, and scanned the conference area for any sign of Chuck. She had her cell set to vibrate whenever he was within a close radius, but it never hurt to be hyperaware. This was a dangerous game they were playing, and she knew it.

"He's not here, Walker. Just come sit down."

Sarah brushed her hood off her hair, glancing expectantly at the video monitors, but they stood blank. "What's this about? He's expecting me."

"I know he is." Casey had his regular piece disassembled on the table and was methodically cleaning each part, not really meeting her eyes, his voice brusque. "He's already been by here this morning."

Sarah nodded impatiently. "And?"

"Your little trip up to the resort for the weekend? Already packed for it?" He was trying to make his voice conversational, rubbing the barrel of his gun with a cloth, but that tone was still in his voice, and Sarah was beginning to feel extremely irritated. Because fear wasn't an option.

"Yeah."

Casey glanced up, then. "He's gonna propose to you, Walker."

Sarah finally sat down, abruptly, in the seat opposite him. "Oh."

Casey nodded. "Oh."

--

Beckman and Graham had been very proud of their plan.

After the incredible conclusion of Chuck and Sarah's first date, they had come to Sarah with a proposition: a long-term cover assignment, by far her favorite, but as Chuck's girlfriend. She could serve as his bodyguard. At the right time, she could "stumble" onto his work with Casey and become an unofficial part of their team. Since all her assignments to that point had been deep undercover, Chuck shouldn't be able to flash on her. He would grow to trust her. He would grow to love her. And she would be able to persuade him to do things he was unsure about, to do what they needed him to do.

They said it was only if they weren't able to get the Intersect out. And they never talked about the end of it.

Sarah didn't ask, because she already knew. Once the government was done with him, there would be no breakup. There wouldn't have to be.

--

The first week of it was very hard. She very carefully constructed her legend and learned it by heart while she mourned Bryce, and it was easier because she and Chuck had a few dates, and her objective was to keep him interested in her. It wasn't difficult. She generally had no trouble seducing a man once she set her sights on him, but Chuck could barely believe that she kept coming back to see him, that she was so interested in him. When he saw her, he glowed with tentative happiness.

From his sister, she learned how badly his last relationship had gone. From everyone, in fact. Morgan knew about it. Jeff and Lester constantly ribbed him about how much he had to be paying her when they thought she was barely out of earshot. Every time she saw him, she saw him differently; from Casey's accounts of his behavior on missions, from his disproportionate joy over a new video game or software release, from the fumbling, awkward way he tried to flirt with her. He was trying.

And despite herself, despite how she knew it was going to end, she liked him.

--

"Do I look all right?"

Sarah finished arranging her side ponytail and caught Chuck's gaze in the mirror. They were going to the art show. She was going to stumble into his spy life tonight.

And he was actually concerned about her. He kept his hands in his pockets and shuffled his feet and, even though he couldn't keep his eyes off her (and that was the idea; no one would be able to concentrate on anything other than the dress), he kept hedging, asking if she really felt like it, saying it would probably be incredibly boring.

"Seriously? You look fantastic." He picked his keys out of his pocket and started toying with them. "It's just... I mean, we can meet up after. Get a pizza."

She glanced over her shoulder at him. "Are you kidding? I really want to see if you've got any more great moves on the dance floor."

"Well, I kinda know how to tango." He breathed on his nails and buffed them against his coat. "Just a little."

"Then I have to see that." She went over her lipstick one more time in the mirror, grabbed her clutch, and hooked her arm through his.

He always seemed so furtive and guilty when he was on a mission with Casey. At least now that would stop, and she was glad. She was here to share this life with him.

It was then that she knew. It was already too late.

--

The night after they failed to defuse the bomb, the one that wasn't quite a bomb, they made love for the first time, and she knew he loved her. She knew he wanted to take this step in their relationship, that it hadn't been her seductive powers alone that had led them there.

What he didn't know was that since the moment she had grabbed him and drawn his face to hers, she had been debating what she should do, if she should tell one of their bosses and have herself taken off this assignment.

Because it hadn't been the cover. She had thought it was her last moment on earth and she had wanted to kiss him. Beyond anything, beyond thought of consequences or repercussions. And making love was cover, was very much on the list of what she might have to do for this assignment, wasn't supposed to mean anything to her.

She told herself that was true. That when she woke in his arms that morning, to a call to get down to the pier, she definitely wasn't falling in love with him. Wasn't. It was too dangerous.

Even so, the paralyzing shock of seeing Bryce alive, the conflict in her feelings, told her that whatever was going on, it wasn't the uncomplicated, dispassionate act of an undercover agent.

She had been allowed to love Bryce. In no way was she allowed to love Chuck. Under no circumstance. He was so far off limits that he should be entirely off her radar.

But he wasn't.

After Bryce, it had been bad enough. But now, she wasn't even able to imagine what she would do if— when this was over. How she'd be able to pick herself up off the floor and go on.

It would be so much easier, she thought. If she'd been allowed to tell him the truth from the beginning. If he knew that their relationship was only cover, that she was along only to keep him safe. At least, then, she wouldn't feel like she was being torn apart.

She'd never felt so close to him as she had when she'd woke in his arms. He was trusting her more by the day, and now, if he ever found out... oh, if he ever found out. That this was nothing more than a convenient lie, the most convenient way for the government to keep him under its thumb.

Bryce had been so much easier.

And if Chuck knew her, really knew her, he'd never love her. He only loved her for the lies she told.

She'd never hated her job so much.

--

On the outside, her life was good. She taught an advanced martial arts class early every morning, limited only to other local agents, to explain her skills when she accompanied Chuck and Casey on missions. Half the nights of any given week, Chuck was at her place, slowly introducing her to the entirety of all his bizarre nerdy obsessions (thankfully, she'd been able to make out with him during most of the Star Trek movie marathons), bringing over pizza or burgers or Chinese. He had his own toothbrush and his own drawer and she was very careful to keep her assorted weapons well out of his sight. She'd spent every major holiday with Chuck and his sister, enjoying it far more than she let herself admit. So when he'd suggested that they spend a few days at a ski resort, just the two of them, she'd only hoped that he wouldn't flash on anyone.

Part of her was afraid, though, of spending so much time with him, just the two of them, with little possibility of work getting in the way. She enjoyed it too much.

"Has Casey been teaching you some awesome ski tips?" Sarah asked playfully, digging in the bowl of popcorn between them. Their hands brushed and she felt the awareness of him tingle up her arm, her spine, straight through her.

"He says I'd break every bone in my body if I tried," Chuck laughed, punching the menu button. "With commentary or without?"

Sarah rolled her eyes. "I know it's fascinating for you to hear how many hours it took to put the makeup on, but..."

"I know, I know." He cued it up. "Let me guess, you learned how to ski rings around people when you were five."

"You mean you didn't see me in the last winter Olympics?" Sarah teased him, kicking her shoes off. "So I need to pack my ski suit, huh."

"There's actually a suit?" Chuck asked in feigned innocence.

"Odd, huh." Sarah scrubbed her hands on her napkin and casually rested one on Chuck's arm.

"Don't think I don't see what you're doing."

Sarah kept her gaze on the television a beat longer. "Hmm?"

"You, sweetheart, are trying to get out of watching Star Trek VI."

"Am not. I love... whatever this is."

"Do not." He crooked a finger under her chin and tilted her head toward him. "And that's okay. I'm really, really excited about going on vacation with you. Just having some time without Casey and... missions and everything. Just us. I love you."

Sarah let herself melt. Every single time, she told herself that it was possible to resist it, and she had to believe that. "I love you too," she said softly, tilting her head invitingly toward his.

He really was too easy.

But then apparently so was she.

--

And here they were, standing in the front door of a palatial suite, enormous. The cold rain that had been falling in LA was snow here, great drifts of enormous flakes, all eerily silent. The bed looked so inviting that Sarah wanted to run to it immediately and launch herself into it, all pillowy cloudy softness wrapped in slick satin. The fireplace in the middle of the room was stocked and crackling to itself, leaving a halo of heat, and the amazing view with all its wide windows, so white it was faintly blue, made her feel cold just looking at it.

She had found the ring in his luggage and stared at it, barely breathing, her mind entirely blank.

No one had ever proposed to her before, and it wasn't real now, but she could see it, and it hurt, how much she wanted it. She wanted it to be real.

Chuck moved and Sarah came out of her reverie, moving aside so the bellhop could bring their bags into the room. He kept catching glimpses of her out of the corner of his eye, a small smile on his face, and there were butterflies in her stomach. She had half a dozen nightgowns packed, a ski suit she knew she'd never unpack, three utterly gorgeous gowns Chuck hadn't yet seen, and, well tucked away, a set of throwing knives. Just in case.

She didn't know what she was going to do.

The bellhop left and Chuck swept her into his arms, and Sarah tipped her face up to his, a soft smile on her lips.

"This is going to be the best weekend of our lives," Chuck vowed, smiling down into her eyes. "I can feel it."

Sarah couldn't believe her eyes were wet. "Me too," she whispered.

If she told him, she'd break everything, the trust she had spent years building, the love he felt for her. She'd be taking it and breaking it in her hands. She didn't know if she could fix it, after that. And if he didn't love her again, after, it was no more than she deserved.

And if she didn't... she didn't trust herself to do what she had to do.

"Champagne and strawberries," Chuck said, smiling, and went to the phone. Sarah looked down at her bare fingers and followed him, pressing down the receiver under his fingers.

"What is it? Are you okay?"

Sarah smiled at him, waiting for it to make sense, waiting for the fluttering to stop. Maybe it never would.

She took her hand off his. "Make it Cristal."