About this "The Simpsons" episode:

The Simpsons - Homer the Vigilante is the 11th episode of season 5 and number 92 overall in the series.
A crime wave hits Springfield, caused by the elusive cat burglar and Lisa's saxophone is stolen, so Homer agrees to try to get it back. The police are ineffective, so Flanders creates a neighborhood watch group, which Homer takes charge of. However, Homer's incompetence causes the vigilante group to commit more crimes than it prevents, and they are unsuccessful in catching the cat burglar. With the help of Grampa, Homer discovers that the burglar is a charming senior named Malloy. Malloy is arrested, but he tricks the citizens of Springfield into thinking he has hidden millions of dollars and escapes during the ensuing rush to find the money.