Sometimes, it only takes one action to change everything – or to spoil what had seemed to be an iron-clad alibi. So it was on that Friday afternoon, as one man's cover story was about to blow up beyond saving, leaving three other people to either twist the knife, try to put the pieces back into something that might pass muster, or to question whether they knew their best friend at all…

The door signal buzzed just as Jon was coming out of the shower. "Perfect timing," he muttered, as he tossed on his robe, threw a towel around his shoulders. Max Forrest had already kept him late today, to talk about the Vulcans' tour of the engine room yesterday and hint more strongly than ever that maybe it was time for him to pick another Chief Engineer.

And now, he was going to be late, just because Trip's sister Elizabeth, who seemed to be here a hell of a lot more often than Trip was, had lost her pass code for the third time in the nine days she'd been in San Francisco. If she wasn't also a hell of a cook -

The woman on the other side of the door hadn't had a very good week at all, and that was the understatement of the century. All of her machinations to get Trip Tucker back on her hooks had failed. She'd done everything she could to get a rise out of him at that ridiculous jazz club of his, but he'd obviously already decided that that damned mystery woman of his was a better place to put his attention.

And now, she couldn't even find him. If she could, maybe he'd let her explain – not that she had any intention of telling him the truth. Oh, no. He wasn't the type to understand about Maurice, and the thing they'd had for the last few years. It wasn't cheating, because she and Trip had never said they were exclusive, and she'd known Maurice twice as long as Trip. But he wasn't going to see it that way, she just knew it.

But she'd gone over her story again and again, and it was perfect. And she'd finally found out he was staying with his friend Jon because he'd gotten into some kind of trouble.

Of course, if this friend of his didn't open the door -

"Come on in!" Jon called out from his room. Better if he took the time to get dressed and think through what he was going to say. He didn't want to snap at Trip's kid sister, but he also didn't know exactly why she was staying here in the first place. Sure, Trip was sharing "Natalie from Pensacola's" hotel bed these days, but why couldn't Lizzie Tucker get a room of her own?

"Uh, hello?" Elizabeth came up the hall to see a beautiful woman at Jon's door. She hadn't known he was with anyone – or, if he was, it seemed like maybe he was a lot more into that linguist he'd gone to see in Brazil. His eyes had lit up when he mentioned her, but he'd also said she was Japanese, and this woman was blonde.

"Hello." The woman half-turned her head to study Liz, then went back to the door. "This thing made some kind of signal, but I don't know how it works."

Well, that meant that Jon was asking her in – or, a hell of a lot less likely, Trip was. But her brother wasn't likely to be here. He'd let Jon think he was holed up with a girlfriend, but she knew better. When things went south for Trip, he didn't go looking for love. He went looking for something to fix, and he always had. "An engineer all the way down to his toenails," Dad had always said. And Mom had invented a name for the types of things he did when something was bothering him. "Tripification."

"Can you help me with this?" The woman's tone was peevish, and Liz realized she'd been staring at her while she thought this through the way Trip had taught her when she was barely more than a baby.

"Sure – sorry. I was distracted." She gave her best Tucker grin, and stepped up to let the other woman in, happy she'd finally memorized the passcode.

Natalie stepped inside when the door opened, looking around for the one person she wanted to see – and not seeing him.

Jon came out of his room, still toweling his hair. Lizzie wouldn't care if he was in his leisure clothes. "Lizzie, you've got to get a handle on that passcode. What's going to happen if you forget it when I'm not – " Lizzie was there, but so was another woman – a well-dressed, slender blonde. "Oh, I'm sorry. I didn't realize you brought home a friend." Damn. Now he'd called his place her home, which was going to make it a hell of a lot harder to ask her to find another place to stay.

"I don't know her. I'm Natalie, and I'm here to see Trip."

"So you're the famous Natalie from Pensacola? I thought Trip was with you."

"I haven't seen him in –" The woman paused, and changed course. "In a week."

"Oh, damn." Elizabeth wished she was the engineer right now, so she could think of a way to give Trip another alibi or shore up this one. But her brain worked better in blueprints.

Jon Archer, though, had good instincts. He looked at Natalie, then stared straight at Elizabeth. "I have a feeling there's someone here who knows a lot more about Trip's whereabouts than either one of us. Spill it, Elizabeth."

Natalie looked at the other woman – competition? How many women was Trip seeing, anyway? This one turned bright red, and mumbled something unintelligible.

"What's that?" asked the man with the towel around his neck.

"I'm not sure."

"Elizabeth."

"Look in your Engine Room."