Georges Simenon, writing autobiographically, once confessed his desire to drop out of society, to sever family ties and disassociate himself from his friends. His empathy with misfits is reflected in Simenon's police superintendent Jules Maigret.

When Maigret learns that a bum's murder is in reality an assassination, he becomes deeply involved in what without him would have been left as an unremarkable event. Maigret must discover the identity of the man who had been living under the Seine bridge, then find out why anyone would want him dead.