“Get up, John,” Sherlock says, in a tone that has John jerking upright in bed, immediately, and grappling for his gun in his bedside drawer, even as he says, “Sherlock, what is it?”

Incomprehensibly, Sherlock simply says, “Voldemort.”

After the eventful Christmas in Harry Potter's fifth year at Hogwarts, his godfather gave him a badly wrapped package. Inside was something Harry could use it to get in contact should the need arise, Sirius said. Harry resolved never to use whatever it was -- he would not put Sirius in danger. When later that year Harry was shown Sirius in terrible danger, he did not think of using Sirius's last-minute gift. Hermione, however, did. This is the story of what happened after that.

War is coming, and Narcissa is scared for Draco. So she turns to the only person she can think of – Sirius Black.