Some sailors manage to capture a monster off of the coast of Ireland and take it back to London to show if off in a circus. The Mother of the monster surfaces, and begins a rampage to rescue her baby.
I think that this movie is too often dismissed as "Just another Godzilla ripoff", as it is a pretty decent monster movie (It also has more in common with King Kong, anyway). It isn't without its flaws, though. The film is extremely dull at points, especially when the human characters are on screen, debating what to do with the monster that they have captured. The film is really saved by the monster sequences. Any time that the monster appears, it is easily the most exciting parts of the film. The Monster suit looks great, and the miniature sets are incredible for the time. The scenes of city destruction are terrifying, and look almost apocalyptic, with a red hazy sky, lit up by fires and the constant bombing of the monster by the military, and filled with the angry roars of the mother monster.