A Sound of Thunder
In Chicago, 2055, the Time Safari company offers the ability for people to hunt dinosaurs in the past via time travel technology. As a precaution against the potential change of the past, the company preys only on the dinosaurs who would otherwise die of natural causes and keeps the clients from stepping off the designated path. Because of the dangers of interfering with the time line, the company's activities are vocally attacked by Sonia Rand, the developer of the time machine software TAMI, who feels scorned for not receiving credit and fears they may alter the past through their activities.
A trip with clients Eckels and Middleton goes afoul when the gun carried by team leader Travis Ryer fails to go off. The dinosaur, an Allosaurus, rushes the group, scattering the clients. Ryer kills the dinosaur, regroups the clients and returns to 2055, unaware that Middleton had stepped on a butterfly. The next day, they hear reports of global increases in temperature and humidity, and Ryer observes a sudden increase in plant life. On their next trip, they find that the Allosaurus they intend to hunt is already dead when they arrive and the volcano erupting much sooner. They quickly return and report the changes, and the government shuts down Time Safari to investigate. Ryer learns from Rand they are being struck by "time waves" that cause drastic alterations to the city as they pass due to something that happened on a previous expedition. Ryer and Rand narrowly escape a building after a time wave causes the appearance of thousands of beetles and a tree bursting through its structure. Rand warns that more time waves can be expected, and each will affect more advanced life forms, people being the last.
They return to Time Safari to try to fix what has gone wrong along with the government. They are struck by another time wave that leaves the city without power and now covered by dense vegetation. Evaluating the machine's logs, they find that the Eckels/Middleton expedition had come back a few grams heavier and that the bio-filter was turned off. They recognize that they can use the time machine to go back to intercept their past selves so as to prevent whatever happened, but will only have a few seconds to act, and so must work to figure out who they need to stop. The Time Safari finds their equipment and gear free of anything, so Ryer and Rand lead a group through the city - now filled with evolved and deadly Baboonlizards and other new hazards that kill some of their party members - to find Eckels and Middleton. Eckels is safe but asserts he remained on the path, while Middleton, poisoned by the new wildlife, takes his life before they can stop him. However, they are able to find a dead butterfly on the sole of the suit he used for the safari. The party makes it back to Time Safari after more time waves hit, now finding the time machine partially underwater and unusable. Rand obtains the hard drive containing the TAMI software with plans to use it with the nearby university's particle accelerator as a substitute time machine.
Ryer and Rand are the only two survivors once they finally make it to the university, Rand noted that the appearance of simian-like Babboonlizards from the latest time wave means the next one will wipe away humanity. Rand prepares the accelerator and stays behind while Ryer goes through the time portal, just as the last time wave hits turning Rand into a humanoid catfish-like creature. Ryer catches up to the previous expedition, catches Middleton to prevent him stepping on the butterfly, tells Jenny the bio-filter is off at the same time asking her to give his earlier self a recording of the events he has witnessed. The expedition returns without incident to the future they had left. Ryer shares the footage with Rand.
alternate reality, stupid, boring, flashback