- "Long time sis." - Lex Luthor
- "Did you always know?" - Tess Mercer
- "Why do you think I recruited you and treated like were my own flesh and blood." - Lex Luthor
- "You used me." - Tess Mercer
- "Semantics. I'd say dear old dad did most of the abusing." - Lex Luthor
- Finale, Part 2
Tess Mercer and Lex Luthor have a complicated relationship that majorally started after Lex disappeared and Tess discovered that Lex was spying on Tess. It was later revealed that they're siblings as Lionel Luthor was their father.
It's unknown when Lex first met Tess. Lex sent Tess and a group of other employees from LuthorCorp to gather viruses (possibly for Project Mercury). When Tess and her co-workers returned to their site, an explosion destroyed the base. While the others escaped, Tess was left for dead. Lex went into the facility and rescued Tess, who was extremely grateful and felt indebted to Lex after this.
After Lex learned Clark Kent's secret from Brainiac disguised as Kara Kent, Lex contacted Tess and asked her to run LuthorCorp for him in his absence. Her dedication to him was apparent as she came to Smallville immediately to carry out his orders to kidnap Lana Lang after she recovered from her coma that Brainiac induced her into. After Lex disappeared in the Arctic Circle and after the Fortress of Solitude collapsed on Lex and Clark, Tess gained control of LuthorCorp and all of its subsidiaries.
- "I did everything you ever asked. You've seen it with your own eyes, and apparently, with mine. But not anymore. I hope you watch with rapt attention as your bank accounts close, and you lose all contact with the outside world. Goodbye, Lex. I loved you, you son of a bitch." - Tess Mercer to Lex Luthor, Bulletproof
Tess went to the Arctic Circle to search for Lex after his disappearance. She had clearly learned a lot from Lex as she presented herself to people in a very similar manner. She eagerly looked for clues of Lex's whereabouts and soon discovered that he was in fact alive.
When she met Lana, she seemed to be jealous of her previous marriage to Lex, indicating her love for him. Lana revealed to Tess that he had injected tiny cameras in her optic nerves and had been spying on her for some time. Tess was devastated by this news and confronted him in a mirror via her optic nerve transmission. She confessed her love for him, which quickly turned to hatred. She then announced his death in the Daily Planet and arranged a merger with Oliver Queen's Queen Industries, Lex's biggest rival.
Lex was clearly angered by this, as he hired the Toyman to plant a bomb in LuthorCorp Plaza during a board meeting with intention to kill Tess and Oliver. However, Tess was not at the meeting as she was reversing the optic nerve procedure with a plastic surgeon and Oliver was able to survive the blast. Later, Lex was murdered by Oliver using Schott's toy bomb to which Tess showed no sadness.
- "You know I'm actually saving you." - Lex Luthor
- "From what?" - Tess Mercer
- "From turning into me." - Lex Luthor
- Finale, Part 2
Tess woke up in Cadmus Labs after she had died as a result of being burned by Zod. After she came across several clones that were engineered from Lex's DNA, Tess opened a door that released one of Lex's clones that escaped and started to fight with her. This clone recognized her from all the original Lex's memories and said Tess loved him, but Tess continued to fight him. Lex's clone got the upper hand and set Cadmus on fire, much to Tess's horror. Lex's older clone then tied up Tess, knowing that Clark would come save her and wanted her to give Clark a message to meet him at Lawson's Field.
While Darkseid's Apokolips was approching Earth, an alternate-reality Lionel Luthor had his thugs kidnap Tess with the intent to harvest her daughter's heart in order to bring back his son. Although Tess escaped, Lex was revived due to some circumstances outside of her control. At the LuthorCorp Plaza, Tess found Lex and he explained to her that he knew she was his sister all along and that that was why he put her into such a high position of power in LuthorCorp. He also told her that he knew she shot the alternate-Lionel in her escape and after hugging her warmly and telling her he loved her, he impaled her with a blade. As she died, Lex told his sister how he was doing this to save her from becoming like him to which she replied that Clark already saved her from that. She stroked his cheek, releasing a neurotoxin into his body that would erase his memories to protect Clark's secret. With this, Tess had proved that she was loyal to Clark even over her brother and that she could die happily in Lex's arms.
- "Seems you've got a talent for making people disappear." - Tess Mercer
- "That voice." - Lex Luthor
- "What's the matter Lex?...You look like you have seen a ghost." - Tess Mercer
Six months after her death which was declared by Lex as a suicide, Tess appears in front of Lex as a hallucination. She states ironicaly that he has a talent for making people disappear. At Metropolis General Hospital, Lex undergoes an MRI to determine why he is seeing hallucinations of the deceased Tess. The doctor informs him that his mind is healthy. Without a physical reason, the doctor offers that learning that Tess committed suicide might have caused a psychological toll. While finishing with the doctor, Tess appears behind Lex and mocks his unwillingness to reveal the truth behind her death. Lex asks if she's a figment of his imagination or if he's being haunted. Tess recounts her death at her half-brother's hand, says that next she knew she was standing next to him on the street, and that she doesn't appear to be a ghost. Though no one else can see her, Lex is able to touch Tess and pushes her against the wall, demanding to know what she is. Tess offers that if he didn't spend so much time worrying about Superman they could take the time find out.
Inside of LexCorp Plaza, Tess once again appears behind Lex, who has found the information on the Nuerotoxin, and how it causes the patient to form a mental bond with.whomever administered the Nuerotoxin, and so they share one mind, with Tess as a secondary consciousness.
In a S.T.A.R. Labs bathroom, Tess appears to Lex once again, where he admits he can sense her when she appears. He also reveals that he plans to repeat the procedure his team is conducting if it is successful, and even plans to try it on Tess's consciousness. She questions why Emil agreed to the procedure and he admits it took a bit of manipulation to convince him. He then ask Tess just how close her and Emil Hamilton's relationship was and she smacks him, with Lex expressing his delight over finally having a way to remove her. Otis interrupts informing Lex that the procedure is over. He then express his sorrow for her condition to the invisible Tess, much to Lex's annoyance.
A night later, Tess tries to control Lex's movements as he sleeps and is curious whether she will succeed or not and is earnestly hoping so. She manages to lift his finger after trying.
The next day Oliver Queen bursts into Lex's office to accuse Lex of harassing him with those coded emails. When Oliver leaves, Lex notices the time stamps are all from the dead of night. During the night, Otis sees Tess take control of Lex and rises from his peaceful slumber and sleepwalks to his office, speaking gibberish and caressing Otis' face. Then she starts sending out the emails.
During a brief argument with Tess Lex notes that she couldn't figure the typing out, and when Tess asks why he's in a good mood, he points out what's on the news: Superman has been shot, and Batman is on the run. Tess points out her death by his hands, a memory he does not have anymore, but Lex isn't angry over she did, as Luthors are "survivors" and she did what he would've done if the roles were reversed. Lex will now be strapped to his bed, preventing her from doing what she did again. He also notes that Tess might have a connection to Superman, as she hopes he's okay as she watches the monitor where his signal is (from the radiation Lex gave him). At Lexcorp, Lex Luthor wants Tess who is still inside him to tell him everything and if she chooses not to tell him he'll take what he wants to know by force.Lex attempts to tap into the memories of his sister Tess' consciousness trapped in his own mind to determine what she knows about Superman. Using a procedure developed by the former LuthorCorp, Lex appears in the memory of the moment Tess was left in the care of Granny Goodness by their father. The grown Tess materializes to help young Lutessa run from their brother down a long hallway. They manage to barricade themselves behind a door. As Lex approaches, he is called to a red door to exit the procedure. In LexCorp Tower, using the Project Intercept apparatus to go inside his mind, Lex confronts Tess and reveals that his team of neurosurgeons has discovered the area of his brain where her consciousness resides. He makes her an offer: tell him everything she knows about Superman or he will have the doctors damage that part of his brain, effectively killing her off. Tess rejects his ultimatum. Lex awakes and tells the doctors to prepare to perform their procedure the next morning.
Lex angrily surveys the room at LexCorp where the Project Intercept machine once stood. He asks after the security tapes and the night guards, and Otis tells him the tapes were stolen and all of the guards quit. Lex turns to the vision of Tess and she denies having anything to do with it. He realizes that it must have been Oliver Queen. Otis remarks that it would likely be best to postpone the procedure to cause his boss brain damage to kill Tess' conscience. Frustrated, Lex leaves.
At LexCorp Plaza, Lex heads towards his office only to find that the lights aren't working. As he calls for Otis, Superman appears with Lex realizing that he found a way to remove the radiation off him. The Green Arrow and Lois Lane appear too, revealing they are here to take Tess back. Lois slaps Lex knocking him unconscious. As he wakes up, he is help by Otis. He realizes what the heroes did and he asks where is his sister.
Later at Watchtower, Clark, Lois and Oliver stands patience as Emil downloads the conscience of Tess into a computer system making her a hologram.
At LexCorp output, Tess remotely locks the doors preventing Otis to accompany Lex, and outside there are three former employees of LexCorp heading towards Lex. Watching the three men beating up Lex, she discards the option of calling 911 to save her brother.
Lex wakes up at the hospital after the beating. Meanwhile Tess observes the activities of the network cameras monitoring the hospital, where Lex is and she is about to change the medication oxycodone, but she fails because she has to answer to an emergency call and so eventually Lex is discharged and leaves.
Later Tess visits Hank Henshaw at S.T.A.R. Labs to get some advice from him about her obsession to get revenge on Lex. When Lex orders his men to invade the facility and Emil Hamilton gets shot by one of them, Tess tries to call 911 but she fails because as she is informed local communications are jammed by LexCorp. Realising that her brother is behind the attack, Hank advices her to keep her emotions in check.
Tess, while controlling a huge robot, attacks the soldiers sent by Lex in S.T.A.R. Labs and then breaks into the place, where Lex and Otis are. Lex orders Otis to leave the place. Tess then attacks her brother and she is about to kill him, and he even tells her to do it, but at the last moment she reconsiders and ends her connection with the robot, sparing the life of her brother.
|Tess Mercer in Smallville|
|Lex Luthor in Smallville|