She’d lost me completely now. I shook my head, wondering if she was a little mad. “I don’t know what you’re talking about.”

“I need your help,” said Elisabeth Lind. “None of the Germans believe I’ve been sent by their British contact. They won’t tell me anything, and I know why. Felix Baer thinks you’re Calypso.”

How was I supposed to know it was a code name?

“I didn’t do it on purpose—” I gasped. “I didn’t know!”

The disappointment was almost as great as the shock.

Of course Felix Baer hadn’t thought there was anything special about me. He hadn’t left me his message or singled me out because he thought I was clever or brave or connected to the aerodrome. He knew only that his contact was called Calypso, and here was I, fresh out of the Caribbean Sea and able to recognize Mendelssohn.

But I’d still helped, hadn’t I? Without me, B-Flight would never have found those U-boats. I’d helped a little, even if it was unofficial and over now.

“How can I fix it?” I asked. “How can I tell him?”

She shook her head, looking into the fire.

“I don’t honestly know,” she said. “648 Squadron’s dragon of a wing commander is always breathing down my neck whenever I see any of the German prisoners. I have my own commanding officer who’s supposed to cope with this, but he’s in Africa, and I can’t even speak to him. I’m just a deputy—I’m still in training and I feel rather out of my depth. None of those Germans want to talk to me anyway, not with Cromwell there, even if they believed I’m their contact.”

She turned to look at me searchingly. Her expression was softer now, and for a split second I nearly caught why she looked so maddeningly familiar, and then it was gone.

“You believe me, don’t you?” she asked uncertainly, and it was like seeing a big crack opening up in a suit of armor.

I nodded. “You couldn’t know about Calypso otherwise. He called me that the first time he was here.”

“Let me think about what we can do,” she said. “You think about it too. I wish Cromwell wasn’t involved. I wish you weren’t involved—”

That’s when Nancy Campbell barged in without even knocking.

“Aunt Jane’s just gone downstairs on her own without her sticks, hanging on the banister and hunting for hot water bottles,” Nancy said shortly. “So I’ve made one up for her and helped her back to bed. Heavens, Louisa, I don’t pay you to sit about blethering! I shall cut your week’s wages if I have to see to Jane again!”

I opened my mouth to make excuses, and shut it without a word.