Cassian is the son of Murdoc and Amber, two professional killers who met each other on the job.
After Murdoc and Amber split up Cassian was sent to a private school in Switzerland to allow Murdoc to continue his work as an assassin without Cassian knowing what his father does.
In Episode 1×20 (Hole Puncher), it’s revealed that Murdoc (David Dastmalchian) has a son named Cassian (Brady Bond) who attends a private school in Switzerland, unaware of his father’s job. Director of Operations for the Phoenix Foundation Matty Webber (Meredith Eaton) uses Cassian as leverage; threatening to tell him what his father does for a living and implying that Cassian would be at risk if Murdoc’s enemies got to know that he has a son. Though still being incarcerated, Murdoc agrees to help the team so Angus MacGyver (Lucas Till) can impersonate Murdoc and save an innocent target of the Organization.
In the Season 1 Finale (Episode 1×21: Cigar Cutter), Murdoc manages to escape prison after killing a guard.
Murdoc tasers, drugs and kidnaps MacGyver in Episode 2×04 (X-Ray + Penny); demanding the whereabouts of Cassian. He tells MacGyver that he met Cassian’s mother – a woman named Nadia – on the job and killed her right after she gave birth. Despite Murdoc arguing that boys need their fathers, trying to appeal to MacGyver by reminding him how desperately he’s looking for his own father, MacGyver refuses to help and manages to escape trough the sewer tunnels.
In Episode 2×15 (Murdoc + Handcuffs), it’s revealed that former colleague Henry Fletcher turned on Murdoc; offering Phoenix to hand Murdoc over for money. After the exchange, they’re hunted by Murdoc’s old mentor Nicholas Helman (Michael Des Barres). In the end, Murdoc saves MacGyver from being shot and demands to be allowed to visit Cassian before he has to go back to prison. He manages to get Cassian out and flee; killing Fletcher while he lets Cassian wait in the car (since Cassian still doesn’t know about his father being an assassin).
In Episode 3×06 (Murdoc + MacGyver + Murdoc), Murdoc kidnaps and hides MacGyver’s girlfriend Nasha (Sibongile Mlambo) to get MacGyver to help him retrieve Cassian who has been kidnapped by an old enemy of Murdoc. As it turns out, Murdoc lied about Cassian’s mother being dead. In fact, Murdoc and Amber (Sarah Sokolovic) – a professional killer and actually involved in Cassian’s kidnapping – are still married. At the end of the episode, Murdoc spares Amber’s life; demanding that she leaves for good and never contacts Cassian ever again. Murdoc goes back to prison while Cassian is put with another family to take care of him.
Reboot series (recurring character)
2×03 Roulette Wheel + Wire (deleted scene)
2×15 Murdoc + Handcuffs
3×06 Murdoc + MacGyver + Murdoc