On June 20, 1972, Cahill was called by Rufus Carlin. He then ordered Carlin to find and destroy the "doc". He was then called again by Rufus and told to kill the the "Doc". When Rufus called him a third time, Cahill sent a team to assist in taking the Doc out. (“The Watergate Tape”)
In order to stop Emma Whitmore and save the team, Denise Christopher approaches Cahill for help. Still caring about his daughter, Cahill makes a deal where he helps in exchange for immunity and protection for his teenage son. Cahill is able to locate Emma and confronts her in disgust over what she has turned Rittenhouse into before leaving as Denise arrests Emma and recovers the Mothership.
- Benjamin Cahill is Lucy Preston's biological father. He also has an unnamed son.
- As of 2017, Cahill is a pediatric surgeon at UCSF.
- Benjamin Cahill is the Rittenhouse member that threatens Rufus Carlin's family if he doesn't keep on secretly recording Lucy Preston and Wyatt Logan during their time travels.