Ethan Cahill was told about Rittenhouse when he was eighteen and his father caught him with a male lover. This information was accompanied with belt beatings. Since then, Ethan had become ashamed of his homosexuality, and underwent shock therapy to try and "cure" himself of it.
Later, Flynn, Wyatt, Lucy, and Ethan go back to the Lifeboat. Lucy introduces Ethan to Rufus Carlin and explains that they are from the year 2017. They show Ethan the Lifeboat in action when Wyatt, Rufus, and Jiya go back to 2017. Lucy explains to Ethan that she's his granddaughter. Lucy tasks Ethan with being a double agent against Rittenhouse, keeping written records of Rittenhouse.
In 2017, Lucy and Wyatt return to Ethan to find out if he had done what they asked him to do. Ethan kept a piece of paper with the address of the location of all the documents he had recorded about Rittenhouse hidden in a clock.