(Spoilers: High Noon, Silence of the Lambs, Gravity, Alien, Aliens, Almost Famous, Speed, Inception, The Abyss)
“Ticking Clock” is a screenwriting term that refers to some kind of time limit on a story arc. It can be used for a scene, a sequence or the whole movie. The most obvious (and fairly cliché) example is a bomb with a countdown timer on it. The hero has to defuse the bomb before that timer gets to zero!
We can see plenty of similar examples in a wide variety of movies:
In High Noon (screenplay by Carl Foreman) the ticking clock is in the title. The bad guys are coming to town at noon. As the sheriff tries to gather allies to help him face down the villains, we constantly cut to shots of the clock getting closer and closer to noon.
In The Silence of the Lambs (screenplay by Ted Tally) we know that the serial killer keeps his victims alive for several days – thus when a new victim is kidnapped, Clarice suddenly has a time limit to solve the case.
In Gravity (written by Alfonso & Jonas Cuaron) there is the ticking clock of the debris, which comes back around every 90 minutes. Ryan sets her watch to track its approach. There’s also the diminishing oxygen in her suit that provides the tension in the first half of Act Two.
Throughout the third act in both Alien (story by Dan O’Bannon and Ronald Shusett, screenplay by Dan O’Bannon) and Aliens (story by James Cameron and David Giler & Walter Hill, screenplay by James Cameron) we hear a computerized voice reading a countdown to imminent destruction – in the first movie the self-destruct sequence of the ship, and in the second movie that nuclear detonation of the facility’s failing power plant.
Ticking clocks can provide momentum in stories that are in danger of becoming episodic. Almost Famous (written by Cameron Crowe) is a coming of age story about young William going on tour with a rock band to write an article for Rolling Stone. But as the deadline for delivering the article approaches and William repeatedly fails to convince the lead guitarist to give him a crucial interview, the tension ratchets up. William can’t just go along enjoying the adventure – he has to get his article done!
A ticking clock needn’t be a literal clock, of course. The deadline doesn’t even have to be at a specific time. We just need to know that at some point the opportunity for the hero to succeed will come to an end, and we need some way to measure how close we are to that point. For example in Speed (written by Graham Yost) the ticking clock is the gas gauge on the bus running down toward empty. There’s a scene in The Abyss written by James Cameron, where our heroes, Bud and Lindsey, are trapped in a disabled submarine with a leak. The rising water provides a ticking clock, a way to measure how long they have to survive.
You can use intercutting to show approaching danger to illustrate a ticking clock, like the old silent movies with the girl tied to the train track. They cut from the girl, to the hero on horseback, to the train, back to the girl, etc.… will the hero arrive before the train (the ticking clock)?
Inception (written by Christopher Nolan) creates an overall ticking clock for the primary mission with the “kick” that wakes them all simultaneously. The team gets spread out across three dream levels and have to complete their various tasks before the kick pulls them out. The tension is increased when the time gets truncated – Yusuf can’t wait as long as he should to activate the kick, and Saito has been shot, providing another ticking clock: they must finish the mission before he dies.
The team uses a song as a countdown to the kick, allowing them (and us) to track its approach. Any time limit serves as a ticking clock, but you have to find a way to show the audience how much time is left. In the case of Saito, we track his deteriorating health.
Once you’ve established the ticking clock, you can ratchet up tension by throwing increasing obstacles in the characters path. For example, in Inception Yusuf is being pursued by gunmen. The team needs to improvise in the second dream level with the Mr. Charles gambit. And after the others head to the third dream level, Arthur has to keep some security guys from getting to a hotel room. And the biggest obstacle comes when Mal shows up at the medical complex and Cobb can’t bring himself to shoot her.
Does your story suffer from a lack of urgency? Try adding a ticking clock. Got a scene that lacks intensity? Ticking clock. It’s a powerful screenwriting tool.