On February 1, television weatherman Phil Connors reassures his Pittsburgh viewers that an approaching blizzard will miss Western Pennsylvania. Alongside his new producer Rita Hanson and cameraman Larry, Phil travels to Punxsutawney for his annual coverage of the Groundhog Day festivities. He makes no secret of his contempt for the assignment, the small town, and the "hicks" who live there, asserting that he will soon be leaving his station for a new job.

Louisa "Lou" Clark is hired as carer for Will Traynor, a once successful banker and active sportsman now tetraplegic after being hit by a motorcycle. Will's mother hopes Lou's bubbly personality will lift Will's depressed and cynical spirits. Will is initially cold towards Lou. Will's ex-girlfriend Alicia visits and reveals that she is to marry Will's former best friend Rupert. Lou perseveres with Will and, as the two grow close, she learns he is cultured and worldly, in contrast to her simple life spent with her parents or boyfriend Patrick.

Nicolas Mallet is a modest bank employee resigned to social mediocrity for the security that his job gives him. Introverted and dull, with the assistance and under the guidance of a former high school friend, novelist Claude Fabre, he will become a confident seducer, an opportunist upstart with no defined ambition. In the aftermath of the oil crisis, the Bel Ami of the 1970s experienced a remarkable social rise, relying exclusively on women whom he seduced almost unwittingly, while being remotely guided by Fabre. Going to seek power from those who rule him, knowing how to make himself indispensable, he will succeed in his ascent and favor that of his first conquest. It is only at the end of the film that we discover the real reasons behind Fabre's manipulative attitude.

Victor Frankenstein (Leonard Whiting) is a newly trained doctor, engaged to Elizabeth Fanshawe (Nicola Pagett). After Victor's younger brother, William, dies in a boating accident, Victor renounces God and declares his ideal of being able to restore his brother to life. Victor leaves the Fanshawe estate for further medical training. Studying in London, he meets the charismatic Henry Clerval (David McCallum), who has discovered how to restore dead matter to life. Clerval reveals his ultimate plan: to create a new race of perfect beings from the remains of the dead. Clerval persuades Victor to help him achieve his aim. They set to work on creating a perfect human, but Clerval dies of a heart attack before the experiment is completed. Victor chooses to honour Clerval by continuing their work and giving their creation Clerval's brain.

Set in London and the south of England in 1929, the story finds erudite Nicholas, Duc de Richleau (Christopher Lee), investigating the strange actions of his protegé, the son of a late friend, Simon Aron (Patrick Mower), who has a house replete with strange markings and a pentagram. He quickly deduces that Simon is involved with the occult. De Richleau and his friend Rex Van Ryn (Leon Greene) manage to rescue Simon and another young initiate, Tanith (Niké Arrighi), from a devil-worshipping cult. During the rescue, they disrupt a May Day ceremony on Salisbury Plain, in which the Devil appears under the guise of the "Goat of Mendes".

Four years after his adventure in the center of the earth, 17-year-old Sean Anderson is arrested by the police for breaking into a satellite control center in hopes of enhancing a coded signal that could have been sent by his long-missing grandfather, Alexander Anderson.

Mrs Wilberforce is a sweet and eccentric old widow who lives alone with her raucous parrots in a gradually subsiding lopsided house, built over the entrance to a railway tunnel in Kings Cross, London. With nothing to occupy her time and an active imagination, she is a frequent visitor to the local police station where she reports fanciful suspicions regarding neighbourhood activities. The officers there humour her but give her reports no credence whatsoever.

In 2007, Trevor Anderson is a Bostonian volcanologist whose 13-year-old nephew, Sean, is supposed to spend ten days with him. Trevor learns at work that his brother's lab is being shut down because of a lack of funding. Trevor has forgotten that Sean is coming until he receives several messages from Sean's mother Elizabeth. When Sean's mother drops him off, she leaves Trevor with a box of items that belonged to Max, Trevor's brother and Sean's father, who disappeared 10 years before. Sean suddenly takes interest in what Trevor has to say after he tells him about his father, whom he never really had a chance to know. In the box, Trevor discovers the novel Journey to the Center of the Earth by Jules Verne. Inside the book Trevor finds notes written by his late brother. Trevor goes to his laboratory to find out more about the notes. There he realizes that he must go to Iceland to investigate for himself.

In 1880 Edinburgh, Professor Sir Oliver Lindenbrook, a geologist at the University of Edinburgh, is given a piece of volcanic rock by his admiring student, Alec McEwan, who is in love with Lindenbrook's niece Jenny. Finding the rock unusually heavy, Lindenbrook discovers a plumb bob inside bearing a cryptic inscription. Lindenbrook and Alec discover that it was left by a scientist named Arne Saknussemm, who, almost 100 years earlier, had found a passage to the center of the Earth by descending into the volcano Snæfellsjökull, in western Iceland. After translating the message, Lindenbrook immediately sets off with Alec to follow in the Icelandic pioneer's footsteps.

When the spaceship that carries the first successful crew returns to Earth, two of the three astronauts are missing, and the third – Victor Carroon – is behaving strangely. It eventually becomes apparent that an alien presence entered the rocket during its flight, and Quatermass and his associates must prevent the alien from destroying the world.