Norman Pitkin, a milkman employed by Grimsdale's Dairy, a tiny family business, delivers milk from a cart pulled by Nellie the horse. One morning he is shocked to find that all his empty bottles have been smashed and that the powerful conglomerate, Consolidated Dairies, has taken over much of his milk round.

Pitkin confronts Austin, a Consolidated Dairies milkman, who is not interested in his complaints, so Pitkin visits Walter Hunter, General Manager of the dairy, at his home. Pitkin gesticulates angrily at Hunter, who is busy cutting the grass. Hunter accidentally knocks Pitkin's hand on to the lawnmower, and the mower speeds away, with Pitkin clinging on, destroying Hunter's garden. Hunter chases Pitkin away with a shotgun.

Returning to Grimsdale's Dairy, Pitkin finds that Mr. Grimsdale is more interested in his romance with the housekeeper, Gladys, than in business matters. Finally, Grimsdale telephones Hunter, who angrily slams down the phone. He orders Austin to ensure that Grimsdale is put out of business within a week.

Austin, claiming that he is sorry for breaking their milk bottles, presents Pitkin and Grimsdale with a box of apples for the horse. Norman feeds most of the apples to Nellie, but they are doped, and the horse becomes ill. Norman is forced to deliver milk using a cumbersome hand cart. In an altercation with Austin, he is knocked down. The handcart rolls on to a level crossing and is smashed by a train.

Pitkin, disguised as a vicar, antagonises Hunter as he attempts to play golf. Hunter finally recognises Pitkin and angrily chases him away.

Grimsdale marries Gladys and decides that the dairy must economise by sending Nellie to an old horses' home. Sadly, Norman leads the horse away; but, in the middle of the night, the horse returns to the dairy.

Visiting Consolidated Dairies' headquarters to accept their competitor's offer of a merger deal, Grimsdale and Pitkin demand half of the combine's business and that Grimsdale be appointed chairman. Hunter angrily orders them to leave.

On their way out, Grimsdale gets stuck in a lift. Pitkin mistakenly gets the impression that the building is on fire. Picking up a broom to smash the glass on a fire alarm, he accidentally opens a hatch on a smoke purifier machine, flooding the building with smoke. Thinking that the building is on fire, staff dash towards the exit.

Fire engines arrive and firemen enter the building. The fire chief is concussed when he falls down a lift shaft. Norman, under the mistaken impression that he has been left in charge of the situation, puts on the fire chief's uniform and assumes command, ordering that the water be switched on. He loses control of the hose and numerous people are soaked with water.

Finally, Mr. Grimsdale is rescued. Hunter and the fire chief, discovering that there is no fire, advance menacingly towards Norman. He jumps from a window, ending up in the driving seat of a fire engine, which he accidentally drives into the side of the headquarters, causing giant cracks to appear.

A large crowd of people, gathered outside the building, listen as Norman speaks out about Consolidated Dairies' scheme to shut down Grimsdale's Dairy. The chairman of Consolidated Dairies is ashamed and embarassed by this outburst and promises to leave Grimsdale's Dairy alone, provided Pitkin leaves Consolidated Dairies alone.