In the dim light the moon provided, Marjie searched in her bag. Her hand clutched the innocent-looking pen that, on touching the ink-release button, flicked open to reveal a sharp, deadly blade. When she showed it to Sibbie, Sibbie nodded and did the same.

The gate creaked as they opened it, freezing them to the spot for a moment. Without opening it any further, they held it still while they squeezed through it, then Sibbie held the gate while Marjie moved the wooden wedge into place. This done, they crept across the yard and began to ascend the wooden steps, grateful for the sound of the rustling branches of the tree that stood in the yard next door, as it masked the tiny creaks of their progress.

As they neared the top, voices came to them; one was Madame’s distinct tone. Speaking in German, she was giving every detail of the forthcoming mission – details they hadn’t yet been provided with.

Marjie knew what they had to do. Without thinking about the horror of it, she signalled to Sibbie, who gave the thumbs-up sign.

With her heart pounding, Marjie grabbed the door handle. A moment of doubt assailed her. Never before had they killed in close quarters. The horror of shooting the German soldiers came to her, but then so did the thought of her comrades being ambushed and killed.

When she flung the door open, two shadowy figures turned towards her. ‘What? Who?’

Blotting out Madame’s terrified voice, Marjie leapt forward and, in an instant, had stuck her knife deep into the woman’s heart. Looking up, she saw that the German had backed off towards the wall. Sibbie dashed by her, but he had recovered and grabbed Sibbie’s arm, bending it backwards. Her cry of pain, and seeing the German go for his gun, spurred Marjie on. Stepping over Madame’s dead body, she lunged forward. Her knife stabbed into his heart.

‘Quick, Sibbie. We have to get our things and get out of here.’

‘No. That would implicate us and surround us with suspicion. The mission isn’t taking place for another week, so that gives us time to let HQ know that it has been betrayed.’

‘You think we should stay here? But—’

‘Yes. We mustn’t be suspected of carrying out these murders. If we are, our cover is blown. We have to burn our coats in the big incinerator by the shed, then clean ourselves up. Madame has a number of coats – we can take two of them. Then go to the door and scream the place down, as if we have just discovered Madame and this other man dead in the attic.’

Marjie knew Sibbie was right. Shaking from her reaction, her mind had gone into flight mode, but now she could see the sense in braving this out.