Small-time crook known as “The Spinner” leaves an envelope with Matt Scudder only to be opened if he is killed. He is then killed.
The contents of the envelope is the blackmail material Spinner has on three people. Believing one of these individuals was pushed too far he just has to figure out which one and let the others off the hook.
Matthew Scudder is both a complex and simple character with a clear moral code that drives through everything.