Dear Sam, she read, Don’t … what? It was impossible to see. She would need to have it properly analyzed. They’d decode it in seconds at the lab.

Frustrated, she tucked the pad and pen into an evidence bag and continued the search.

“There’s no phone here. Not even a charger,” she said. “No laptop, nothing.”

She went through to the kitchen again, to see if she’d missed something in there. There was nothing plugged in and nothing in the cupboards but a box of out-of-date cereal. When she opened up the fridge, a puff of rotten air escaped, and she shut it hastily.

“This place. It’s not like there’s anyone living here, not really. She’s been sleeping here maybe, but not much else.”

“Certainly looks that way,” said Atkinson. “I think she must have come back regularly to check the post, though. There’s nothing here older than a week.”

“Did you find anything interesting?”

“Only one thing, but I’m afraid it won’t give us much to go on.”

Us, she thought, experiencing a begrudging little glow at the fact that Atkinson had thrown his lot in with her despite the risk to himself if he went along with her off-the-record antics. He handed her a yellow envelope handwritten in blue ink. On the back, when she closed the flap, a capital S had been drawn where an old-fashioned seal might have been.

“What was in it?”

“Nothing. Just the envelope. But if you look closely, there are some words on the inside where the ink has transferred.”

The postmark was smudged, impossible to read. “I can get this to the lab. They’ll be able to tell us more. And they’ll be able to lift prints, hopefully.” She slipped it into an evidence bag and folded the flap closed.

“The lab?”

“Yes, the lab. You remember. Where we send things to have them analyzed.”

“I know that. I just meant how are you going to square that with Thrupp? What code are you going to use?”

All official evidence was coded with a catalog number that indicated where it was found, at what time, and what case it related to. There were no exceptions: if the lab couldn’t categorize it, they wouldn’t process it. Joanna was well aware of the procedure. She’d planned to deal with that when she had to. Solutions would present themselves, she was sure of it.

“Just leave that side of things to me, will you?”