The film is set in Sweden in the year 1846. Albert Vogler arrives with his "health theatre" at the home of the middle-class Consul Egerman. With him are his disciple Aman-Manda, his manager Tubal, an herb-collecting old woman, Granny, the coachmen Simson and the actor Spegel whom the motley crew found en route in a state of delirium tremens. Spegel has collapsed and is presumed dead.

At the Egerman house, Vogler, who is mute, is examined by Dr. Vergerus, the town's medical officer. The doctor dismisses the muteness as a hoax. The humiliated Vogler joins the rest of the gang in the kitchen, where Tubal and Granny are selling love potions to Sofia, the cook and to Sara and Sanna, two maids. Sanna is frightened by the group and is consoled by Granny who sings her an old ballad. Sofia is attracted to Tubal and Sara flirts with Simson. Suddenly the deceased Spegel comes sweeping into the room and grabs a bottle of alcohol.

In Vogler's bedroom. Aman-Manda, now revealed as Mrs. Vogler, is visited by Dr. Vergerus. Vogler walks in and is furious to see Vergerus there with his wife. When they are left alone and he has removed his wig and false beard, Vogler confesses to her his fear of the public whos scrutiny make him feel powerless.

The next day a performance takes place in the Egerman's living room. It consists of two parts; Mrs Starback, wife of the Chief of Police, is hypnotised and speaks of her husband's gauche manners and the Egerman's coachman, Antonsson, also in a trance, who is fettered with an invisible chain. Powerless, in a panic, he strangles Vogler and aghast at his action dashes out and is later found hanged. Dr. Vergerus decides to perform an autopsy unaware that Vogler, who was only pretending to be dead, has substituted his own body for that of Spegel, who is now truly dead.

The autopsy takes place in the attic where Vogler plays a number of terrifying tricks on Vergerus until the doctor screams and tumbles down the stairs. Later, when he meets the unmasked Vogler he denies having been affected by the "séance" in the attic and continues to ridicule the troupe. However the tables are turned when Vogler and his companions are summoned to the Royal Palace. Granny and Tubal decide to remain but Sara joins the troupe. The end sees Vogler's Health Theatre departing in triumph to the sound of grand music suggestive of pomp and circumstance.