Gwendolyn Hayes (Jeri Ryan) aka “Titan” is the member of an organization called “Codex”. She is the sister of Ellen MacGyver (Scottie Thompson) and therefore sister-in-law of James MacGyver (Tate Donovan) and aunt of Angus MacGyver (Lucas Till).
Ellen died when MacGyver was 5. James didn’t deal well with her death, becoming engrossed in his work at DXS. He eventually left when MacGyver was 10, leaving him in the care of Harry MacGyver (Michael O’Keefe).
The Phoenix Foundation and its predecessors have a history of teaming up soldiers with scientists. Many of the operatives at Codex are former OPI/DXS agents; disillusioned about the state of the world. Their ultimate goal is to initiate “File 47”; the activation of engineered disasters around the world to trigger a chain reaction, resulting in the complete collapse of human civilization so it can be rebuilt.
After the events in the Season 3 Finale, the Phoenix Foundation was disbanded and the team members were stripped of their high-level clearances. In Episode 4×01 (Fire + Ashes + Legacy = Phoenix), Russ Taylor (Henry Ian Cusick) as the new owner of Phoenix convinces MacGyver to get the team back together. During the first few episodes, they encounter an organization called “Codex”.
When tracking down Elliot Mason (Peter Weller) in Episode 4×08 (Father + Son + Father + Matriarch), James reveals to MacGyver that his cancer is back. They find Mason, but soon realize that it was a trap and that Gwendolyn is indeed still alive. She tells MacGyver that File 47 was actually his mothers idea; trying to convince her nephew to join Codex and “reset the world” together. At the end of the episode, James sacrifices himself so MacGyver can escape; pointing out beforehand that his son is the more valuable asset and the only one who can stop Codex from destroying the world. Gwendolyn, Scarlett (Amber Skye Noyes) and the other Codex mercenaries with them pack shop and relocate.
In Episode 4×10 (Tesla + Bell + Edition + Mac), Scarlett and her team is sent to retrieve items left by Nikola Tesla. Following Team Phoenix into a mine, her team is stunned by Tesla’s weapon Shiva. In Episode 4×12 (Loyalty + Family + Rogue + Hellfire), Gwen intercepts MacGyver’s morning run and tells him that his mother didn’t die from cancer, but was killed by the same people that wanted Gwen dead. To make it look like he defected and joined Codex, MacGyver helps Scarlett breaking out. With the help of Riley Davis (Tristin Mays), they retrieve Shiva and bring it into Codex’ headquarters.
In the Season 4 Finale (4×13: Save + The + Dam + World), head of Codex Leland (Tobin Bell) questions MacGyver and reveals to him that he once tried to recruit Russ Taylor. Leland is impressed by MacGyver, but later realizes that he’s still loyal to Phoenix. Leland fears that the fondness for her nephew and for Scarlett might be too much of a distraction for Gwendolyn, so he wants them to be killed off. While Riley and Mac can escape, Scarlett and the other Codex members in the warehouse don’t. Gwendolyn is furious with Leland and sacrifices herself to prevent Codex from detonating a nuke inside a dam. Leland and the rest of the surviving Codex members disappear.
Reboot Series (recurring character)
4×08 Father + Son + Father + Matriarch
4×12 Loyalty + Family + Rogue + Hellfire
4×13 Save + The + Dam + WorldMENTIONS:
4×07 Mac + Desi + Riley + Aubrey
4×11 Psy-Op + Cell + Merchant + Birds