Thomas Markinson is the commander in Syphon Filter and commands Gabriel Logan & Lian Zing on every mission of the virus
Markinson commanded them to find the viral bomb in Washington, D.C, where Erich Rhoemer & the Black Baton lead a assault on the city. Gabriel Logan finds a fake main bomb at a subway, leading to a explosion, he find & wounds Mara Aramov and Markinson commands him to find the bombs in the Washington Park. the CBDC disarms them everywhere.
Logan heard that Edward Benton was working for Black Baton in a exhibition center, he heads there to find Benton, and kills him. and interrogates Markinson on the way out. he takes Logan to Rhoemer's base in Kazakstan and while planting the bombs on every gasoline tank, he kills Gabrek. and the base is destroyed while him & Markinson make a getaway. while Logan picks up communication from Lian, she is now taken hostage by Rhoemer. and sent his attack chopper to kill him. he escapes again.
Markinson sent Logan to infiltrate the stronghold to inject some patients with a antidote. in deeper in the stronghold, he found Lian alive and she's infected with Syphon Filter. Markinson is negotiating secretly with Rhoemer for the Syphon Filter virus to the Agency. while Gabe makes his way to Rhoemer, he meets with Markinson about the virus. while he answers about the missile, Markinson is violently shot in the back of the head by Rhoemer and he lands dead in the bottom of the missile.