Sirius Black
Sirius knew where Peter was. Or rather, he knew where Peter was supposed to be hiding.
If he wanted to catch Peter, he needed to hurry before that rat went underground. Who knew how many rats resided in London's sewers. And if Peter decided to hide in muggle London, then it would be even more difficult to track him down.
"Hagrid," Sirius said. Across the room, Hagrid finally pulled out a basket from the rubble and set baby Harry inside it. "Hagrid."
"Yeh?" Hagrid asked, pulling up Harry's down throw blanket from under an armchair.
"Take my motorcycle," Sirius offered. "It can fly." Speed is of importance and who knows how long it will take Hagrid, who can neither apparate nor fit inside a normal floo to reach Frank and Alice's place. Better he fly there. On that note, Sirius wonders, how did Hagrid reach James' place so quickly? Even before himself?
"Thanks, Sirius," Hagrid smiled and Sirius shook that thought out of his mind. "How do ye use it?"