Hopalong Cassidy, foreman of the Bar-20 ranch, is summoned to Silver Center by his friend, Dan Forbes, who suspects that the vigilante group of which he is a member has been corrupted because they have been foiled at every attempt to stop robberies. Forbes confides in Henry Logan, the town leader and head of the vigilantes, who, unknown to Forbes, orders him and Hoppy shot. Forbes survives his injury and Hoppy gets the better of his assailant when he is accosted in Gunsight Pass. Hoppy shoots the man, Ed Stone, and leaves him for dead, then he and his companions, ranch hands Lucky Jenkins and California Carlson, continue into town. Knowing that the criminals are expecting him, Hoppy tells Forbes and his daughter Helen to pretend that they do not know them. After Hoppy, Lucky and California prevent a robbery attempt planned by Logan, Logan's gang fights back by terrifying the community with raids, fires and vandalism. Hoppy and Forbes arrange for a wagonload of silver to be switched to entrap the criminals. When the silver seems to have disappeared, however, suspicion falls on Hoppy, until they find that California loaded the wrong boxes onto the wagon and the silver is still at Forbes's house. Hoppy, Lucky and California finally corner Logan and his gang at their hideout and during a gunfight, Hoppy is shot in the shoulder. He then tricks the gang into surrendering by exploding bullets in a fire, which makes it sound as if they are outnumbered. Logan and his gang are arrested, and Hoppy, Lucky and California leave the Forbes ranch to return to the Bar-20.