A Sound of Thunder is a science fiction film released in 2005, and directed by Peter Hyams. The film was planned originally for a 2002 release. However, flooding in Prague (where the production was filmed) and other financial difficulties—- including the bankruptcy of the original production company during post-production—- resulted in a delayed release. A Sound of Thunder is based loosely upon the short story “A Sound of Thunder” by Ray Bradbury. The film is about “time tourists” who accidentally interfere too much with the past and thus completely alter their present.
Businessman Charles Hatton (Ben Kingsley) has recently offered a time tourism service. For an extraordinary price, Time Safari will take clients through a wormhole to the past to hunt dinosaurs. Scientist Travis Ryer (Edward Burns) is the leader of these expeditions, along with several other guides. The following protocols are set out:
Don’t change anything in the past.
Don’t leave anything behind.
Don’t bring anything back.
To further ensure that Earth’s evolutionary timeline will not be disturbed, only creatures that are already doomed—such as dinosaurs about to die in a volcanic eruption—can be killed. The participants must wear helmets with sealed faceplates (like astronauts) and use rifles that fire frozen-nitrogen bullets that melt, leaving no trace. The wormhole itself creates a path that physically separates the party from touching the ground, and on which they must remain.
On one excursion, the guides are escorting a party of wealthy clients that includes two friends. One of the men, who is extremely nervous, is surprised by a prehistoric butterfly which he tries to shoot when it flutters close to his helmet. He learns that his weapon will not fire, as all safari patron weapons are tied remotely to Ryer’s. He alone can fire first, thereby deactivating the safety feature on the tourists’ rifles.
The group gathers before a large tar pit, waiting for their prey. As scheduled, they are charged by an Allosaurus, but the safety on Ryer’s rifle does not deactivate and nobody is able to fire. Panicking, the two wealthy tourists run off to seek cover. Ryer and the guides distract the dinosaur, while quickly exchanging gun parts in order to slay the beast. The party returns through the time portal. Unseen, a footprint of tar on the path indicates that someone has stepped off it.
The next day, Ryer notices significant climate and other small changes around him. On the next expedition, Ryer and a new party of tourists arrive to slay the Allosaurus. As they wait for the creature to emerge, Ryer checks his watch, realizes it is late and that the Allosaurus should have already arrived. Instead, they find it has already died. Furthermore, the volcano, which is supposed to erupt after the explorers return to the future, is already in the process of erupting.
The Federal agency that oversees temporal travel opens an investigation and shuts down Time Safari in order to review protocols. Ryer seeks out Sonia Rand (Catherine McCormack), the original developer of the time travel technology and the computer (TAMI) that controls the jumps. She believes that Time Safari is essentially playing with fire and she eschews her previous association with company.
Because the past has been changed, a series of time waves sweep across the present. The first wave produces changes that drive the two from Rand’s apartment. Rand explains that the sequence of changes will not take effect at once, but instead will spread out like a series of ripples on the surface of water. Moreover, they will proceed in order of evolution: first the non-living physical environment will reset, then the vegetation will change, then wildlife, and finally humans.
Under supervision of the temporal agency, Time Safari sends Ryer back to fix the past with Rand’s help. When he arrives, he discovers he is in the American Southwest and about to be trampled by an Apache tribe on horseback. Ryer ducks out of the way, but sees that another time wave is about to hit. He leaps through the wormhole, but just as he exits, the wave hits, causing all power in the Time Safari facility to go out. When back-up power is restored, the building and the city are covered in dense vegetation.
One of the scientists, Payne (David Oyelowo), discovers that the team arrived just over a gram heavier than when they left. It is also discovered that Hatton has bribed a government administrator to allow the shutdown of a costly “bio filter,” which screens out the transfer of organic matter. The team leaves the company building and find the two clients battling baboon/dinosaur and bat/pterodactyl re-evolved hybrid creatures as well as predatory plants. They learn that one of the tourists stepped on a butterfly, bringing it back to the present, and critically altering the evolution of life.
Another time wave hits just before they reach the time portal. Finding it no longer works, they decide to try to get to a university possessing a particle accelerator, which can be modified to function as a time machine. Eventually, only Ryer and Rand are left alive. Rand manages to send Ryer back 65,000,001 years to dodge the time waves, after which he is sent forward one year to the point when the original explorers traveled into the past. In the present, the final time wave hits and Rand is turned into a catfish-like humanoid.
Ryer tells Jenny (Jemima Rooper) about everything that will happen in the future. He stops the tourist from stepping off the path and killing the butterfly, and thus the future is saved. Back in the present, Jenny gives Ryer the video of the alternate Ryer who saved the future. He visits Rand to show her the video, hoping that together they will be able to put the time company out of business.