“You know, there was something strange that happened. Sam’s a real loner. I’ve never seen him with anyone before, so I suppose I wasn’t expecting it. But the other morning, we heard a scream, coming from over there, where he was moored. I thought it must have been someone passing by, a gongoozler. We get families walking on the towpath all the time. Especially on Christmas Day. Morning walk with the family, you know. It’s like Paddington bloody station round here.”

“You heard a scream?”

“Yes. Very high-pitched scream. I never imagined it could be from Sam’s boat. I didn’t get a chance to ask him whether or not he’d heard it too, because later he’d gone, which in itself isn’t unusual. Anyway I didn’t connect the two things. But now that you’re here, maybe it does make sense. What’s he done, run off with someone’s wife?” The woman seemed strangely delighted by the prospect. Bent over, wrapped in her blanket, Harper couldn’t help thinking she was just like the witch in so many of the fairy tales she’d read as a child.

“Who do you think was screaming?”

“I don’t know. I got the impression it was a child, from the pitch of it.”

“Not an adult?”

“Well, could have been a woman, I suppose. Do you think he was strangling her? Is that why you’re looking for them? Is it a murder inquiry?”

Jo kept her face completely still.

“You say that Sam’s boat left on Christmas Day. Do you know which way he went?”

“That way,” said the woman, pointing to one of only two routes out of the wharf. “North. Very itchy feet, that one. Always on the go. I never thought he might be a criminal, though.”

Joanna noticed the boarding ramp from the woman’s boat, which rested on the towpath. There was grass growing all around it. “You don’t move, though?”

“Not me. I pay for this mooring, so I don’t have to. Some boat people like to be able to move. That’s part of why they choose to live onboard. Very small world though, especially in the winter. I’ve seen Sam here a few times. He’s not one for farewells. Or hellos, actually. And he’s not a terribly festive chap; no decorations or anything.”

She fingered the wrinkled berries on the holly wreath adorning her cabin door. “It’s always the quiet ones, isn’t it? I never took him for a violent man.”

“Can you show me exactly where he was moored?”

“Just across there,” said the woman, indicating the other side of the wharf, which had space enough for about fifteen boats. “And I wouldn’t bother knocking on any of those other boats. No one’s in. Mostly holiday craft.”