Nikki Carpenter (Tracy Spiridakos) is an undercover CIA operative. She formerly worked as a hacker for DXS until she faked her own death in the Pilot Episode.
She and Angus MacGyver (Lucas Till) were in a romantic relationship for about 2 years. It was Jack Dalton (George Eads) who had introduced them to each other before she joined MacGyver and Jack for DXS field missions under Patricia Thornton (Sandrine Holt).
In the Pilot Episode, the team infiltrates a party in Italy to steal a biological weapon from a terrorist. The mission goes awry, with MacGyver and Nikki getting shot and falling into Lake Como. While Mac survives, the bioweapon is stolen and Nikki’s body can’t be retrieved. Jack advises the team to recruit Riley Davis (Tristin Mays), a hacker who’s currently serving time in prison. Riley manages to track bad guy Kendrick and the bioweapon – and Nikki, who’s apparently still alive and working with Kendrick. At the end of the episode, the DXS packs shop and rises under a new think-tank-cover called the Phoenix Foundation.
MacGyver feels responsible for not noticing Nikki being a mole, and vows to hunt her down and bring her in. All he manages to find is a fake passport and a key Nikki specifically left for him. In in Episode 1×08 (Corkscrew), Nikki encounters him in their favorite diner, pointing a gun at him and asking him to think about a certain DXS mission that had gone wrong.
In the mid-season finale Episode 1×12 (Screwdriver), it’s revealed that Nikki worked undercover for the CIA to bring down the Organization and the mole that infiltrated DXS/Phoenix. As it turned out, Thornton had not only framed Nikki for being a mole, but had also hired assassin Murdoc (David Dastmalchian) to take out MacGyver.
MacGyver asks Nikki if she is going to come back to Phoenix, but she reminds him she still has to take down the terrorist group.
Reboot series (Season 1)
1×01 The Rising