Worldly-wise Fred (Spencer Tracy) takes naive Jimmy (Franchot Tone) under his wing at boot camp, helping the gun-shy youth he calls Hayseed adapt to the army. The two friends see action in the trenches, and Jimmy uses the marksmanship he developed to wipe out enemy machine gunners. Jimmy gets medals...and Rose (Gladys George), the nurse who agrees to marry Jimmy after she erroneously believes Fred has been killed in battle. Postwar, Jimmy is no longer reticent about guns and secretly is a mob hit man. Then Fred inadvertently encounters his old army pal, setting in motion events that put Jimmy's marriage and life in the balance.