Besides, all the ships in all the world knew the dangers, with unrestricted submarine warfare declared in January. They would be on their guard. They would travel in convoys.

But still, an average of fifteen per day would still sink. Margot dropped the list of U-boat targets into the basket and tried not to do that math. Fifteen a day, average of thirty days in a month, four hundred fifty ships every month for the nine months since the declaration, equaled four thousand fifty ships lost.

The door opened, and Margot looked over to see Admiral Blinker Hall stick his head in. “How did the night go, chaps?”

De Grey motioned to Margot and, presumably, the decrypt she’d just carried over. “De Wilde cracked the cypher. Haven’t had time yet to apply it to whatever has come in since.”

The Director of the Intelligence Division—fondly referred to as DID by everyone under his command—sent her an approving smile. “Well done, Margot.” He blinked a few times and moved his gaze to take in de Grey and Culbreth. “Will you be leaving, then? Knox was just behind me, and Adcock too.”

Culbreth nodded and stood, placing his hat over his blond hair in the same motion. De Grey smoothed his tormented locks back down to hide the hours of frustration his fingers had left in them. “I need to speak to Dilly first, but then I shall, yes.”

Hall arched his brows her way. “Margot?”

“I’ll wait until my mother arrives before I go.” Otherwise she might miss her on the walk to their flat, and then Maman would worry all day. No matter how many times she’d made the trek on her own, no matter how old she got, still her mother worried.

Her prerogative, Maman claimed.

A useless argument, Margot knew.

“Very good.” Hall moved away a step, then pivoted back again. “I have an appointment first thing this morning with Lady Hambro and a new recruit. If by chance they arrive before the secretaries, could you direct them to my office?”

“Of course.” Margot smiled at her superior and then kept it in place as her colleagues followed him out—Culbreth apparently aimed at the stairs, de Grey turning the opposite direction, toward Room 53, which Dilly Knox had claimed as his domain. Among the first cryptographers to be recruited to Room 40, Knox had already been firmly established here when Margot arrived. Though absent-minded about practical things, he had a head for mathematics. Margot had liked him from the start.