Jimmy Kelly, who can't hold on to a job because of his hot temper, finds his calling as a process server. He serves process on a gangster and exposes a criminal conspiracy while trying to stop his long-suffering girlfriend from taking a vacation with her lecherous boss.

Argumentative Jimmy Case loses yet another job when he argues with, then punches, a passenger on his city bus. When his sweetheart, Eleanor Rogers, learns of this latest firing, she breaks their engagement. After an attempt to use his fists in a boxing ring ends in a knockout, Case makes up with Eleanor and agrees to meet her boss, lawyer H. Herbert Oakley, to discuss a possible career in law. Case starts night school but soon loses his temper and hits the teacher. After being served with a summons for the fight by his friend, Sammy Kohn, Case decides to take up process serving. Kohn arranges for a job for Case with his boss. While serving papers on a dancer, Grace Clarice, a free-for-all starts. Case escapes through Clarice's window, leaving Eleanor to fend for herself. This is the last straw for Eleanor, who decides to join Oakley on a business trip to Montreal. Case and Kohn are selected to serve summons on "Sweet Sue" and "Number Seven" as part of the district attorney's crackdown on city graft, but first they have to find out the identities of their victims. Case discovers an address and goes to serve the papers on Sweet Sue, who turns out to be a over-sized gangster. While Case is there, he discovers that Oakley is Number Seven. When Kohn tells him that Eleanor is going away with Oakley, he and Case race to the train to stop them. Case rescues Eleanor just in time and serves Oakley. The next day, Eleanor is brought to the city building and taken to the Marriage Licence Bureau, where Case is waiting for her.