“Cause of injury?” Challice suggested, with a slight tang of disappointment. “When they wave those hooked sticks around, there’s a lot of force.”

“According to the chap who found him, ma’am, his head was already smashed,” the constable offered hopefully. Challice beamed at him. Clearly they both wanted a murder.

“We’ll need to have the coroner’s views on the head wound, and if he died from that or drowning,” Aaron said. “We’re not going to find any traces of his movements on the bank with all this rain and people fishing him out.”

“Sorry, sir.”

“Not at all, Constable.” Aaron stood, wincing at the creak in his knees. “We’ll need a trawl done for witnesses, and the coroner’s report. Meanwhile, let’s find out a little more about Mr. Marks.”

The address on the business cards was close by, in Finsbury, a cramped dark building. There had been no keys on his person, but the building manager, who gave his name as Gillan, explained that he rented out his rooms as offices, and had spares.

“Mr. Marks dead,” he observed, searching through a drawer. “There’s a thing.”

“You don’t seem upset.”

Mr. Gillan shrugged. He was a skinny man who Aaron suspected bought gin before food, his grey complexion limned with red capillaries. “Didn’t see much of him. Didn’t want to. Not a line of work I like.”

“What did he do?”

“Stuck his nose into people’s business, that’s what,” Mr. Gillan said. “No offence. He was a private detective.”

“Was he indeed? Let’s have a look at his room, then.”

Marks’ office was on the first floor, but didn’t benefit from light or air, being a miserable dark space that was one dirty window away from being a broom cupboard. “Funny place to rent for a man with a nice gold watch,” Challice remarked as they looked around.

“Nothing wrong with my premises, miss,” Mr. Gillan said, the rebuke rather watered down by taking two goes at ‘premises’.

“It all needs a jolly good scrub,” Challice informed him severely.

“Excuse us, Mr. Gillan,” Aaron said, and waited for the landlord to withdraw. “Challice, look at this.”

He’d found a shelf of notebooks, identical cheap ones with thin ruled paper, each filled with the same handwriting and dated on the front. It crossed his mind, a fleeting thought, to wonder what Wildsmith might make of the hand.

“Marks’ records,” he said, pulling himself together. “This should be useful. If...” He went to the far end of the row, checked the book, started working backwards, frowned. “They’re all dated, but the last one I can find is three months ago. Have a look round for the recent ones, will you?”

They both looked. They went through the small room, the desk drawers, the piles and shelves and every scrap of space, and when they’d finished, Challice drew a long breath. “Nothing.”