I'm looking for a story I remember reading, but I don't remember the title or author, and only pieces of the plot. This is what I can remember:

It starts with a boy and a girl (siblings?) and the boy is walking on the sidewalk when gangsters (mafia?) run into him and he somehow loses his bag and has theirs, without knowing it. They then have to hide, which they do with the help of a Japanese (?) seamstress. Eventually they are captured and imprisoned in a more or less abandoned warehouse owned by the gangsters, and a rather homocidal woman from the gang is planning to kill them. They start a fire, which eventually engulfs the building, and the woman in trying to push one of the children into the fire ends up falling in herself. Meanwhile the police have come and have captured the gangsters, and the children smash a window in the warehouse, and the firefighters haul them out through the window.

Does this ring a bell?