“If I pop down for a moment, will you keep an eye on Nicole?” she asked, and he said, “Sure.”

She walked slowly down, her steps echoing. At the bottom, she found herself in a concrete-walled room full of packing cases. A door straight ahead was bolted shut so she took another door on the right and straightaway knew she was in the murder room. Great gashes had been hacked in the plaster of the back wall, exposing the crisscross laths beneath. Piles of rubble lay in front and there were dark patches on the floor that made her shudder. It couldn’t be blood, could it? Not so long afterward. All the same, she trod carefully to avoid it.

The walls had been papered in a stripy pattern that had faded now, and they were studded with holes that could only be bullet holes. Loads of them. The killers must have fired and fired and kept firing. For a moment Val felt as if she could smell the gun smoke and hear the family’s terrified screams in that enclosed space. The atmosphere crackled with something awful.

Her chest felt tight and her breathing became shallow. Was there enough oxygen? Which was the way out? There were some double doors at the back of the room and she felt momentarily disoriented. Were they the ones she had come in through? Panic took hold until she spun around and saw the other door: it must be that one. The Romanovs couldn’t escape that way because their murderers were lined up in front of it.

She hurried into the concrete storeroom, then ran up the steps two by two into the sunlight. At first she couldn’t see Bill and Nicole and feared something had happened to them; then she noticed them peering at a wall.

“It’s a blue butterfly,” Nicole whispered as she got close. “Isn’t it pretty?”

“You all right?” Bill asked, noticing the expression on her face.

She grimaced. “No sugarcoating at all.”

They made their way back to the main entrance, where the bored receptionist was reading a magazine and barely looked up as they headed for the stairs to the upper floor. On the landing they stopped and listened but there didn’t appear to be any other visitors. As they walked into the first room, Bill whispered translations of the words on his plan.

“This was the study of the commandant of the guards, first Avdeyev then Yurovsky,” he told Val.

There was faded purple wallpaper with gold palm leaves on which hung a doleful stag’s head. Cushions were scattered across a daybed, and on one side there was a large leather-topped desk. Val walked around slowly, drinking in the details and scribbling notes in a spiral-bound notebook.