Curtis Knox is an immortal doctor, warrior and killer in the WB/CW TV series Smallville.
He served as the main antagonist in the seventh season episode "Cure".
The man known as "Curtis Knox"'s past was shrouded in mystery. At some point in his life, he acquired immortality and lived through the ages fighting Mayan warriors and Crusaders but he always survived.
By the 1800s, Knox moved to London where he killed several prostitutes whom the public dubbed him as "Jack the Ripper". During World War II, Knox traveled to Germany and became involved with the Nazi party. At the turn of the millennia, Knox came to America and married a woman named Sophia.
During his eternal life, Dr. Curtis Knox became a brilliant neurosurgeon who developed a cure for meteor freaks by simultaneously removing all of their memories of having powers. In actuality, he was obsessed with trying to make his wife Sophia immortal by harvesting kryptonite-infected body parts from meteor freaks that he would then transplant into her body.
One of his patients was Sasha Woodman, a metahuman who could control bees, returned to Smallville and ran into Chloe Sullivan who confronted her and asked how she escaped Belle Reve. Sasha claimed that she was cured and said she doesn't remember the last six years because she underwent a procedure by Dr. Curtis Knox. Sasha leaves towards her car and was approached by Dr. Knox himself. He tells Sasha she has "something he needs" and presses a chloroform-soaked handkerchief to her face. Sasha passes out and Knox drags her away.
Lex met Dr. Curtis Knox in the library of the Luthor Mansion. They have been working together to cure metahumans, but Lex asks him about some questionable tests Knox has been running on Level 33.1 subjects that Lex never approved. Knox blows off his concern, claiming that science and medicine only advance when risks are taken. Lex asked if Knox knew where three missing patients were and Knox suggests that their memory loss might have made them disappear. He thinks Lex erased their knowledge of Lex's responsibility, but Lex claims he was helping them by eliminating disturbing memories and Knox exits.
In an elaborately-decorated bedroom, Knox is seen caring for an unconscious woman. She is surrounded by jars containing green glowing liquid and life-support machinery. He kisses her and reports that he has found another "puzzle piece". He puts on an apron and approaches Sasha, who is strapped to a table, struggling to get free. Knox selects a surgical instrument and extracts an organ from Sasha's abdomen, killing her.
Chloe Sullivan researched Dr. Curtis Knox at the Daily Planet. She then went to his clinic and announces that she wishes to be cured of her meteor-rock infection. Lana Lang had also done research on Knox discovering his work with meteor-infected people. Lana reports that Knox claims he can cure meteor-infection with brain surgery.
The following evening, Dr. Knox is disposing of Sasha's body at the Smallville Fertilizer Plant when Lex catches him. He tells him that he won't let him kill anyone else. Knox claims that he has cured them and made them forget what Lex did to them. He reveals that he only decided to work for Lex because a chosen few have something he needs. Lex pulls a gun and when Knox advances, he shoots him in the chest six times.
Knox falls but to Lex's astonishment, he gets right back up, unharmed. He knocks Lex out with a flashlight and is about to deliver another blow when Clark super speeds onto the scene. He knocks Knox into a power line and gathers Lex up to take him to safety. Lex wakes up in the hospital, surprised to see Clark at his side and asks him about Knox. Clark spits that Lex is no better than Knox and regrets having to take his life for Lex.
Lex tells him that Knox is, in fact, immortal — he attacked him after Lex shot him. He also tells him that Knox is murdering his patients. Chloe arrives at Knox's facility but is suspicious that there are no staff members present. Knox reports that she has elevated meteor-rock concentration in her heart. Chloe realizes that she is in danger but when she tries to run, Knox catches her and chloroforms her.
Chloe wakes up strapped to a table, next to Knox's wife, Sophia. Chloe offers to heal Sophia with her meteor power, but Knox explains that she is not sick; he is tired of watching his lovers grow old and die, and intends to take Chloe's heart out and put it in his wife to make her immortal.
Clark gets to Knox's office but he is already gone. Lex arrives shortly afterward and shows Clark research he's done that proves that Knox has been around since at least 1675. Clark found Knox's pocket watch. Lex recognizes the inscription matches the Victorian arms, where Knox lived in the 1920s.
Clark super speeds there just as Knox is pressing a knife to Chloe's chest. He pushes him across the room and unbuckles one of Chloe's hands before he is overcome by the jars of glowing green fluid. He and Knox fight brutally, destroying the medical equipment in the room.
Clark finally collapses but Knox abruptly stops fighting when he realizes that Sophia has flat-lined. He cradles his dying wife as Chloe frees herself and pushes the meteor rock away. Clark recovers and they watch in stunned silence as Knox cries over his dead wife.
Clark later handed Knox over to the Martian Manhunter. He imprisoned Knox in a holding facility on Mars, somewhere even an immortal would have difficulty escaping from.