|Portrayed by Gemma Massot|
|Episode of Death:||Collusion|
|Cause of Death:||Overdose and drugged by Trask|
|Parents:|| Trevor Mathis † (father) |
Harriet Mathis (mother)
|Siblings:||Aiden Mathis † (brother)|
|Also portrayed by:||Samantha Connolly (image in Lineage)|
|First appearance:||"Lineage" (image)|
|Latest appearance:||"Collusion" (video)|
Colleen Mathis was the elder sister of Aiden Mathis. She was abducted by a Russian mobster Dmitri Bladov in 1993 , a week before the bombing of flight 197, where his father possibly inadvertently played a role in (another possibility is that it was taken hostage to force him to help terrorists). She was never heard from again, but Aiden, who later enlisted with Takeda, made it his mission in life to find it.In 2006, Dmitri told Aiden that Colleen was probably dead, but Helen Crowley claims that the Initiative kept Colleen alive in case they ever needed Aiden's services.
In "Collusion", Helen Crowley uses Colleen as leverage to get Aiden into doing their bidding, which is, at this point, to kill Victoria Grayson. They sent Aiden videos of Colleen being interrogated and, as his 24-hour deadline for Victoria's death approaches, gave him more threatening videos, one in particular being a clip of Colleen being given drugs which she apparently enjoys. When Emily convinced Aiden not to kill Victoria since he would be kept under the Initiative's thumb if he did, they finally sent a video of her apparent death, which was set up to look like an overdose. Angry at Emily for talking him out of fulfilling his assignment, Aiden still had hopes that Colleen was alive.
In "Union", Aiden asks Nolan to take a closer look at the video footage of Colleen being drugged and killed. He checks the metadata and finds that the video was created six years ago (around the time Aiden killed Dmitri), not three days ago as Helen led him to believe. Using a serial number from an electric meter seen in the background, Nolan finds the abandoned warehouse in Jersey City where it was filmed. With Nolan's help, Aiden and Emily later find Colleen's autopsy photo and her grave, proving her death.