NASA hacker, and he recruited Walter to work for the government. He was Walter's handler and father figure for five years until he asked Walter to design some tracking software for "humanitarian purposes". However, the software was really used to bomb Baghdad and kill 2,000 civilians. Walter broke all ties with Cabe, but was continuously tailed thereafter by Homeland. Cabe is an outgoing man who seeks to help those he loves, and seems to have a lot of trust in his people. In the show, Cabe demonstrates this trust to his surrogate son Walter, with whom he had difficulties in the past. Walter even states outright near the end of season three that out of all the crew, Cabe trusts him the most. Cabe is a very forgiving person, given Walter's actions in the past, but when Allie, his girlfriend, betrays Sylvester by posting humiliating videos of him under the instruction of her boss, Cabe cannot forgive and ends the relationship. With Sylvester’s encouragement, they later get back together. Riley B. Smith as Ralph Dineen (recurring season one, main seasons two-four) is Paige's son; he is initially believed to be a troubled child before meeting and interacting with Walter, who tells Paige that he is actually a genius. He interacts well with the team, and on occasion, assists with cases. Ralph was born to Paige Dineen and Drew Baker, and unbeknownst to them, was a genius. His father left when he was young, saying he was going to go see a movie, so Ralph had little memory of his father. Later, when Ralph had a sense of math, he started counting how many movies his dad would have seen until the present day. He has an IQ of 200. Recurring Camille Guaty as Megan O'Brien (season 1–2), Walter's sister and Sylvester's wife, who had multiple sclerosis, a condition that Walter sought to "fix" to repay the favour of her always being there throughout his childhood. She died in the episode "Arrivals and Departures" after suffering complications due to her disease. Brendan Hines as Drew Baker (season 1), Ralph's biological father, who is a struggling minor-league baseball player. Daniel Zolghadri as Young Walter (season 1) David Fabrizio as Paul Merrick (seasons 1–2), the Director of Homeland Security. After the events of season 1, Merrick was demoted and reassigned as Homeland Security's liaison to NASA. He dies in the episode "Da Bomb"