Lillian is a patient in a psychiatric ward in the 1950s. Cole speculates that she is Primary, which she does not confirm nor deny.
Lillian murders her parents and two younger siblings, something she later claims she did to save them from the impending destruction of time. She is then committed to a mental asylum, where she goes at least 34 years with no visitors.
As the effects of time collapsing begin to worsen, Cole momentarily finds himself walking around while all of time has stopped. The only other person who appears to be unfrozen is Lillian, where she warns him that "it's not over." He finds her in a mental asylum. She tells him that the Red Forest has not been stopped, and tells him to go to the Pine Barrens and bring back what he finds there. When he returns with a Red Forest leaf, she tells him that he can use it to send his mind back in time to 1957 and prevent the final paradox. When he hesitates between choosing to prevent the paradox and undoing his and Railly's two year relationship, or enjoying his remaining time with Railly and allowing the Red Forest to devour time, she tells him that death can be undone, but love cannot. She also warns him not to go to Titan in 2045 to save Ramse, saying it is a cycle that should not be changed.
- Lillian is portrayed by Madeleine Stowe, who played Kathryn Railly in the 1995 film Twelve Monkeys, on which the series is based.
- The line that Lilian speaks to James Cole "and have a merry Christmas" is a reference to a line of Madeleine Stowe in the film Twelve Monkeys.