Sue a Little Heroine by L.T. Meade

When so many strange things were happening, we may be sure that Father John was not idle. He had hoped much from Peter Harris's knowledge of the byways and dens and alleys of Westminster. But although Peter was accompanied by the sharpest detectives that Scotland Yard could provide, not the slightest clue to Connie's whereabouts could be obtained. The man was to meet more detectives again that same afternoon, and meanwhile a sudden gleam of hope darted through Father John's brain.

What a fool he had been not to think of it before! How glad he was now that he had insisted on getting the name and address of the brave fireman deliverer from Connie on the previous night!