<P> By the end of season two, Lana and Clark slowly try and start a romantic relationship, but fear backlash from Chloe because of her personal feelings for Clark . Just as the two give in to their feelings fully, Clark unexpectedly runs away from Smallville in the season two finale . At the start of season three, it is shown that Lana, alongside the Kents, has been spending her time searching for Clark; she ultimately finds him in Metropolis thanks to Chloe's help . Clark's actions in Metropolis force the two to rethink their relationship in the season three episode "Phoenix", and Lana eventually begins a new relationship with Adam Knight (Ian Somerhalder), a guy she met while in physical therapy after being trampled by a horse in season three's "Asylum". By the season three episode "Crisis", it is discovered that the relationship Adam attempted to form with Lana was just a ploy so that Adam could investigate Clark . </P> <P> Season three's "Forsaken" reveals that Lana, in order to move on with her life, applies and is admitted into a program to study in Paris, France . Season four shows that Lana, while in Paris, began a romantic relationship with Jason Teague (Jensen Ackles). At the beginning of season four, Lana returns to Smallville after receiving a mysterious tattoo on her lower back, which resembles a symbol on the local Kawatche cave walls, when she touched the tomb of Countess Margaret Isobel Theroux . In season four's "Spell" and "Sacred", the tattoo acts as a doorway for the spirit of Isobel to inhabit Lana's body; each time Isobel takes over Lana's body she sets out to find the three stones of knowledge, which are also being searched for by Clark and Lex Luthor (Michael Rosenbaum). In the season four finale "Commencement", Lana is confronted by Jason's mother Genevieve (Jane Seymour), who is also after the three stones of knowledge, and during a struggle Isobel comes forward and kills Genevieve . The resulting death of Genevieve, who was revealed to have been the cause for Isobel's death centuries prior in the episode "Bound", releases Isobel's control over Lana . </P> <P> During the second meteor shower, Lana witnesses the landing of an alien spacecraft, and two alien beings emerging and killing everyone in sight in the season five premiere . The spaceship becomes Lana's primary focus in season five, officially teaming up with Lex Luthor to discover the mystery behind the ship in the episode "Splinter". When her relationship with Clark hits a breaking point in season five's "Hypnotic", she begins to grow closer to Lex . The relationship with Lex eventually leads to marriage in the season six episode "Promise", but not before Lana discovers Clark's secret and realizes why he has been lying to her all these years . When she learns that Lex set up a fake pregnancy in order to get her to marry him in the season six finale "Phantom", Lana effectively ends the marriage and fakes her own death to escape Lex after he threatens her . She also frames Lex for her murder, to punish him for his betrayal . It is revealed at the start of season seven that her effort fails, but as part of the "settlement" of their divorce, Lex makes sure that Lana does not go to jail for her actions . </P> <P> With Clark's secret no longer an issue, the two begin a real relationship in the season seven episode "Fierce". Lana becomes obsessed with making Lex pay for all his crimes against humanity, which causes her to develop the Isis Foundation, using $10 million she stole from Lex . The Isis Foundation is a counseling center for kryptonite - infected people, but it doubles as a front for Lana's surveillance on Lex . Her obsessions also begin to affect her relationship with Clark by the episode "Wrath". Eventually, Lana realizes that, even though she loves him, the only way for Clark to help the world to the best of his ability would be if she left Clark and Smallville for good, which she does in the season seven finale . </P>

When does lana find out clark's secret
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