He nods. “It’s possible. I’m twenty-six, so she’s twenty-eight—born 1982. Your father didn’t disappear until late 1983, right?”

“Yes, but that’s like saying he could have fathered any child in the region born prior to the date of his disappearance plus nine months. I mean, it’s technically possible, but that doesn’t mean it actually happened.”

He extends a placating hand. “I know, I know—believe me, you’re preaching to the converted. But she has it in her head. She’s always had it in her head . . .”

“But why?” The door upstairs is banging at intervals just long and uneven enough for me to think that it might have stopped before each new thud.

“I know, it makes no sense. There is no reason. She just . . . I dinnae ken why. She just somehow got the idea in her head and it never left. I cannae remember a time that she didnae believe it.”

“Does your dad know she thinks this?”

“Christ, no, that would destroy him. Fiona is his wee girl; she can do no wrong. Especially since she produced Callum out of the blue. My dad is gaga for that wee lad. And believe me, she’s smart enough to know which side her bread is buttered on.” His expression is rueful as he says this, but it’s not completely convincing. I suspect Jamie’s ego does not take kindly to being the less favored child. “I’d never tell him. Though it’s been hard over the years; she can be quite hurtful. And with all the other problems she already has . . . You probably noticed her behavior the other night, right?” I shake my head, not sure what he means. “How she was watching you?” I hadn’t noticed that, but then I was busy trying not to be seen watching her, worrying about my own subtlety. I’m so deeply unsettled now that it’s a struggle to stay in my chair; I want to get up and pace. Jamie’s still speaking though. “It’s because she thinks she’s your half sister.” Half sister. The words jolt me. I already have one of those. Do two half sisters make a whole? “And normally she’s fine, really she is, but with you suddenly here, God knows what is running through her brain . . .” He drags a hand through his hair, then takes a deep breath. “I was thinking . . . ach, it’s a horrible imposition, but . . .”

“But what?”

“I thought maybe . . . It’s going to sound nuts, but I thought maybe if we did a DNA test, if we proved to her that the two of you are not related, then maybe she might, I dinnae ken, let it go or something—”

“No.”

“Aye, I figured you’d say that, but please just take a moment to think about it—”