An extortionist (Freddie Jones) hides six time bombs on a cruise liner, the SS Britannic, and demands a £500,000 ransom in return for information on the bombs' locations and instructions on how to disarm them without setting off their booby traps. A Navy bomb disposal team, led by Lt Commander Fallon (Harris), is flown out to the ship and attempts to disable the bombs, while on land a team of investigators led by Superintendent McLeod (Hopkins), whose family are on board the Britannic, race against time to uncover the identity of the bomber.
This film contains examples of:
- Anonymous Public Phone Call: When the bomber rings up to demand a ransom, the police do a Phone-Trace Race only to find it's just a relay, attached earpiece-to-mouthpiece to another public phone which is receiving another call from the bomber's actual location.
- Blatant Lies: When the passengers have to Abandon Ship in very bad weather, a member of the crew assures them they'll soon be picked up. An American politician (being a Consummate Liar) tells him he's full of it.
- Booby Trap: Charlie decides to put an insulator between a couple of detonator prongs to prevent them touching. Instead, the bomb explodes. When Fallon takes a close look with a magnifier at the prongs on his own bomb, he sees there's a thin wire connecting them that sets off the bomb if it's cut.
- Crapsack World: The shipping line would have gone broke years ago if it weren't for a large government subsidy, the ship's captain is having an affair with one of the passengers, the South Asian steward has been on the receiving end of racism his whole life, the bomb disposal team is overworked and underpaid, the cops don't have enough of the proper resources, and the weather on the cruise is miserable.
- Evil Sounds Deep: Averted; the villain talks in a somewhat prissy voice when making his demands, to hide his identity.
- Foreshadowing: Early in the film, a member of the bomb disposal unit named Charlie mentions to his boss Fallon that he's passed on an opportunity to take a different job. Later, while both Charlie and Fallon are disarming two separate bombs, Fallon quips, "Haven't I told you about death? It's nature's way of saying you're in the wrong job." Shortly thereafter, Charlie's bomb goes off, killing him.
- From Camouflage to Criminal: While defusing the bombs planted by Juggernaut, Fallon realises they resemble a particular German Time Bomb used during World War 2, and tells the police to consult a man he served with during the war who has experience with such devices. He turns out to be Juggernaut.
- Heroic BSoD: Fallon has one.
- One-Word Title
- Ransom Drop: The ransom demanded by the bomber is to be left in a certain locker at a bus station. The police stake out the locker, but the man who comes to pick up the money turns out to have been hired to collect it and drop it somewhere else, with no knowledge that can lead back to the bomber. He also inadvertently screws up the bomber's plan when he doesn't have enough money to pay the excess baggage fee (having spent it already).
- Security Cling: There are several Time Bombs on a passenger liner and bad weather prevents anyone from being evacuated. The entertainment officer tries to rouse their spirits before giving it up because no-one is singing along. On confessing his own fear to a female passenger, she suggests that everyone just wants to be held right now. As the band starts to play a Convenient Slow Dance, he asks her to join him on the dance floor, and soon the other passengers follow suit.
- Stiff Upper Lip: Averted; the passengers quickly work out the crew are nervous. When they're finally told the truth, the entertainment officer tries to raise their spirits to no avail, finally giving up and admitting that he's just as terrified — a Convenient Slow Dance works a lot better.
- Time Bomb: An extortionist has six identical, booby-trapped bombs, hidden in various parts of the ship and set to go off when the extortionist's deadline expires (plus a smaller one set to go off at the same time as the extortionist delivers his demands, as proof that his threat is not a hoax), promising the plans to defuse them if a ransom is paid by dawn tomorrow.Fallon and his team para-drop in to try to defuse them.
- Vehicle Title
- Wire Dilemma: In the days before this was a tired cliché, everything comes down to Fallon, a pair of wire cutters, and two wires. At the film's climax, defusing the bomb requires guessing whether to cut the red wire or the blue wire. The police back in London have captured the bad guy, and he tells them to cut the blue wire — so now the question becomes, do you believe him, or cut the red wire? You cut the red wire.