‘Let’s see what this Dr Varma’s got to say for himself,’ he says.

Two minutes later, Silas is sitting with Strover in a bleached-out waiting room, staring at an illustration on the opposite wall of the human brain. Strover is flicking through a copy of Auto Express. Silas started to get more interested in neurology when he set up the super-recogniser unit, learning about the fusiform gyrus, the part of the brain where human faces seem to be recognised and processed. As he begins to trace the temporal lobe, a man comes out of Dr Varma’s consulting room. Silas and Strover haven’t made an appointment to see Dr Varma, but his secretary said he would see them between patients. Silas gets up and passes by the man, who keeps his face averted.

‘Did you clock that?’ he says to Strover, knocking on Dr Varma’s door.

‘Didn’t want anyone to see him,’ Strover says.

They wait for a few more seconds, but there’s no answer from behind the door. A flicker of concern. Silas knocks again and waits, glancing around the empty waiting room. Dr Varma’s next patient has clearly not shown up yet.

‘Dr Varma?’ Silas calls out, head close to the door. His stomach starts to tighten. He looks at Strover, takes a deep breath and opens the door.

‘Oh Christ,’ he says, taking in the scene. ‘Quick, out the front,’ he adds. Strover spins around and runs.

Silas walks forward into the spacious room. An Asian man, presumably Dr Varma, is slumped behind a large desk at the far end. The wall behind his head is sprayed with filigree red patterns. For a split second, Silas thinks it’s one of those strange images that psychiatrists show to their patients. And then he realises it’s blood, from a gunshot to Dr Varma’s forehead. His eyes are open, staring up at the ceiling, as if permanently in awe of the sky.

Silas checks outside the large sash window. A car drives off at speed, chased by Strover, who runs after it for a few yards before stopping. Silas turns away, walks over to Dr Varma and feels in vain for a pulse, scanning the mass of papers on his untidy desk.

‘Too late. Sorry, boss,’ Strover says, coming back into the room.

‘Check his diary with reception,’ Silas says, still beside Dr Varma. He needs a few moments on his own. ‘Find out if his killer made a booking.’

Once Strover has left the room, he pulls out his phone and takes photos of various sheets of paper on the desk, careful not to touch or dislodge anything. Dr Varma’s laptop is to one side, angled towards where he’s sitting. Silas pulls out a hanky and carefully presses the space bar, waking up the screen. Leaning closer, he starts to read, glancing up at the closed door.