A New York cab driver helps an Irish immigrant with a baby locate her missing husband.

An arsonist-for-hire dubbed "Mr. Matches" has been been torching buildings all around the city. Bernard Frank, head of the fire bureau, knows who he's looking for because he's spotted in the crowd at each of his jobs admiring his work. To catch "Mr. Matches" in the act, the department has an ex-con hire him to take down a building they're monitoring. His capture becomes personal after Frank's son is killed in one of the arsonist's fires.