Christopher "Paul" Merrick was the former Director of Homeland Security, who secretly was a spy for China. Merrick joined the Department of Homeland Security, and became its director sometime before 1997.
Merrick doesn't have any faith in Scorpion, questioning their every move and not willing to give them the help they need. He's often butting heads with Cabe Gallo, questioning the efficacy of Scorpion. His stubbornness nearly led to cases not being solved. When Scorpion was trying to locate a bomber while working with Thomas Keeler from FSG, a government organization, Merrick told FSG they had a lead just before Scorpion discovered that FSG was behind the bombing. When Scorpion was assigned to help with a peace treaty meeting between Lithuania, Belarus, and Latvia, Merrick refused to let Scorpion leave after the Lithuanian president was poisoned with snake venom, and Scorpion was trying to find an antidote. When Merrick discovered they had snuck out, he threatened to tell Walter O'Brien the truth about Cabe's involvement in the Baghdad bombings. After the president was revived and the treaty was signed, Cabe said he wouldn't forget Merrick's threat.
When a research facility was threatened by someone who wanted the truth about the Baghdad bombings revealed, Cabe asked Merrick to not reveal everything. Merrick refused, and Cabe admitted to Walter he had known about the bombing, but didn't tell Walter, for fear he would disrupt the mission. The blackmailer is stopped, but Scorpion is left in shambles over the revelation. Merrick mockingly gives Cabe his new assignment, to basically be a nanny at LAX. Cabe refuses to give in to Merrick's satisfaction, and resigns.
Cabe is reinstated by Homeland in the season premiere, and it's revealed that, since Merrick wasn't able to accept the Scorpion team as a valuable asset, he was removed as director. He was replaced by Adriana Molina, who was then ousted of Scorpion when she almost let Sylvester die in prison. Molina was then replaced by
The team eventually sees him again when they're assigned to help with a NASA launch, and meet Merrick, who is the Homeland liaison. Scorpion tries to sabotage the launch when Walter's date, Linda, shows up with a bomb strapped to her and an electronic voice demand that they stop the launch. Scorpion, though, tries to save the launch when they find out there are people onboard the rocket. At the same time, they realize that Merrick is behind the threat, having drugged Linda and constructed the bomb on her. Merrick tries to stop Happy Quinn from saving the launch, but he's attacked by Cabe, and threatens to detonate the bomb. Cabe asks his motive, and Merrick reveals he's been a Chinese spy for years, but when he was removed as director, he needed to find another way to give intelligence to China. He and Cabe struggle, and Merrick eventually falls over a railing and hits the concrete ground below, killing him instantly. Scorpion is able to save Linda and the launch.