Primeval - Season 1 (2007)

Eight years after his wife Helen disappeared, evolutionary zoologist Professor Nick Cutter - along with his friend Stephen Hart, his geeky student Connor Temple, zookeeper Abby Maitland, Special Forces leader Captain Tom Ryan, and government officials James Lester and Claudia Brown - discovers that mysterious rifts in time and space called Anomalies are allowing creature from across Earth's history to run rampant in the present; and the group subsequently become a Home Office research team tasked with predicting the Anomalies and containing the ceatures which come through them, and learning more about the Anomalies and why they are happening. However, Cutter secretly has an agenda of his own about the Anomaly operation: as the team investigate the Anomalies, Cutter begins to find more clues that imply his long-missing wife Helen is alive and living in the past on the other sides of the Anomalies. The rest of the team eventually learn of this, and that Helen is indeed alive and in the past, but she has been greatly changed by her time there and her study into the Anomalies, and the team are uncertain which side she is on. Eventually, Helen seemingly allies with the team to find and contain an Anomaly in the past to the future and to combat a deadly predator from the future which is on a killing spree in the present; but while Nick and Helen are searching in the past for the future Anomaly, Nick discovers that Helen only wanted to find the Anomaly and see the future, and after Captain Ryan is killed, Nick returns to the present. However, there, Cutter finds that Claudia Brown has been erased from the timeline while he and Helen were in the past.