When the clock in the lounge struck quarter past one, I almost sobbed with relief and made for the stairs, half running in case anyone should try to stop me. Finally, I reached the safety of the roof terrace with its locked door, and sagged against it, breathing hard, trying to stay calm. This was the part I didn’t like. Everyone at the party had to see me; they had to swear that Langham had been present all night, especially between one o’clock and half past.

Was a murder happening even now? I thought feverishly, peering out across at the city. Was Cabrera dead, lying crumpled in some alleyway, or face down with a bullet in his back? How had Langham done it?

I knelt down behind the parapet, wiping sweat from my upper lip, and checked the pocket watch. Twenty past one. I took the box of matches from my pocket, snapping three before I finally managed to light one and touch it to the waiting fuse. Then, I backed away to the farthest corner, watching it burn down, knowing that from this point on, there would be no return.

The firework exploded into the night, red and gold and white. I stepped to the edge of the roof terrace and threw my arms wide, knowing my figure would be illuminated, in its distinctive white suit. Below in the gardens, people began to cheer and aah, pointing up at me and clapping, yelling, Arthur darling, don’t fall off!

Done, I ducked back down. I had to hurry.

At the bottom of the stairs from the terrace, I ran straight into Hilde.

‘People are coming up,’ she said breathlessly. ‘Quick.’

She hustled me into Langham’s room and locked the door behind her, just as voices echoed in the corridor.

‘Langham,’ a man bellowed, hammering on the door, ‘come out and settle a bet!’

‘I think he’s busy,’ a woman’s voice slurred, ‘or didn’t you notice the bus boy was missing?’

There were sniggers and Hilde threw a look at me. They were too close to the truth. Suddenly, she was kicking off her shoes, pulling the dress over her head. ‘Hold this,’ she hissed. I threw off the hat, ruffled my hair and turned my back to the door just as she opened it, wearing only her slip.

The sniggers ceased.

‘If you’ll excuse us,’ she said, her voice low. ‘Mr Langham and I are enjoying a private conversation. We’ll re-join you in a moment.’

She slammed the door and locked it. We didn’t move, listening to the laughter on the other side.

‘They’re at it again,’ the woman crowed, as they stumbled away back down the hall. ‘Who’d have thought! So much for the cook!’

Hilde was dressing rapidly. ‘It’s nearly quarter to two,’ I told her, my pulse racing. ‘I have to get to the Continental. Hilde, what if he—’