Mark Lynch is the main antagonist of the Torchwood episode "Combat". He is a stressed real estate baron who started an underground club where businessmen fight captured aliens called "Weevils".
In 2006, an operative of the government agency Torchwood, Jack Harkness, is chasing a Weevil when he witnesses a group of men grab it and put it in a van. He and fellow agent Tosh Sato trace the van to a warehouse, where they find the dead body of a man who was attacked by a Weevil. Jack receives a phone call from a man who tells him not to interfere. Later, Jack interviews a man who he suspects was injured by a Weevil, but refuses to say anything because "they" will kill him.
While investigating, Torchwood agent Owen Harper goes undercover to interview Lynch, who is suspected of having something to do with the incident. Posing as an exporter of jellied eels, Owen meets Lynch for drinks at a bar, where he is attacked by a thug who Lynch helps fight off.
Lynch invites Owen over to his house for drinks, where Owen finds a chained-up Weevil. Lynch invites Owen out to see some entertainment, which is revealed to be a fight club. Stressed businessmen like him fight each other to warm up before paying £1000 to go into a cage with a Weevil. Whoever stays in the longest wins and Owen is up next. Owen willingly enters the cage, only for Jack and another agent named Gwen (who were earlier informed of the club's location by a text sent to the dead man's phone) too raid the building and pull him away. Realising that his livelihood is ruined, and not wanting to go to prison, Lynch commits suicide by locking himself in the cage with the Weevil, which mauls him to death.