As she pulled it out a paper-clip caught onto the sheet beneath it. She took the whole lot out and detached the clip; underneath was a small red 1989 diary with thin cardboard covers. It had been doodled on and covered with cartoon faces, but the remarkable thing about it was the name, ornately decorated in felt-tip pen: Della. She knew there was no record of a diary having been found at Della’s efficiency.

Tennison carried her finds back to her own office and flipped through the little book, slowly. It contained misspelled notes, appointments for hospital checkups, lists of cash against rent and expenditure. One entry read “New dress, new shoes, streaks.” There were a number of pages missing throughout the year; they had been roughly torn out, in some cases leaving chunks of paper behind.

Was there also a diary for 1990? Tennison went back and searched Otley’s desk again, but found nothing apart from a near-empty whisky bottle.

She left everything as she had found it, apart from the file and diary, collected her copy of the file from her desk and returned to the Incident Room. She laid the files side by side on the desk and began to compare them, fighting to keep her eyes focusing.

The box room felt airless. Tennison tossed and turned, got up to open the window. She had decided to sleep there so as not to wake Peter.

She lay down again, but kept seeing Della Mornay’s face and hearing Otley’s voice as he told her that Shefford had believed there was another murder . . . Going over and over her conversation with Sergeant Otley she dozed off at last.

At five-thirty in the morning Peter shot out of bed. He could smell burning.

He rushed into the kitchen and checked that everything was off, then followed his nose along the hallway. On the radiator near the door was Jane’s raincoat; the back was singed, leaving a large dark brown stain.

He looked into the spare room. The window was wide open and Jane lay sprawled face down, arms spread wide. He felt as if he was intruding and he gently closed the door, afraid to wake her.

At six-thirty Peter brewed coffee. He was due on the building site by seven. He carried a cup into the spare room.

“Jane . . . Jane!”

“What . . . What? What?”

“Hey, it’s OK, it’s me. Brought you some coffee. There’s more in the pot, but I’ve got to go.”

“Oh, shit, what time is it?”

“Just after six-thirty.”

“Oh, God, I’ve got to get cracking. I’ve got to . . . I’ve got . . .”

She flopped back on the pillow. “I am knackered, completely and utterly knackered . . .”

“So’s your raincoat. You left it on the radiator in the hall and it’s singed. I’ll have to look at the heating when I get home tonight, shouldn’t get that hot.”