Azura Skye ("Zoe...") guest stars as a girl obsessed with Lex. Clark is distracted by Lana's sudden companionship after Whitney pushes her away.

Who is Amy Palmer? Amy is the teen daughter of servants at the Luthor mansion. She is obsessed with Lex, and writes secret love letters to him in her diary. Amy even has Lex's watch, given to him by his mother, which she secretly treasures. Troy, fellow Smallville H.S. classmate snatches her diary, finding out about her obsession with Lex, and berates her in front of her brother Jeff. With a vengeful look in his eyes, Jeff defends his sister against Troy's insults. Later, in the boy's locker room, Troy is attacked by an "invisible force." Clark and Pete find Troy on the floor, as we see a shadowy figure in the steamy locker room.

What's up with Victoria? As she further cozies up to Lex, Amy brings in refreshments. When Lex introduces Victoria, saying she's staying for awhile, Amy purposely spills drinks on Victoria. Lex dismisses is as a mistake, but Victoria tells him Amy has a "thing" for him. Amy later hints at her jealousy to her mother and brother, while her mom reminds her of her "place" in the household.

What's up with Lex? As Lex searches for his missing watch, Clark delivers tulips from the farm to the Luthor mansion. The tulips, for Victoria, are mysteriously overturned and fall. Lex and Clark talk a bit about Lex's relationship with Victoria and Clark's new hope of a relationship with Lana. Clark offers Lex help in finding his watch, and goes in to check the library. He surprises Victoria, who's on Lex's computer, snooping around using his password.

Just then, they hear something upstairs, and Clark, Lex, and Victoria go up to investigate. Behind Lex's bedroom door, there is a shimmering light and the door is shaking. Lex opens the door and is thrown back. Inside the room is a mess, and "LEAVE NOW" has been spray painted on the walls. Later, Lex's father drops in unexpectedly, knowing Victoria is there. He has come to talk about family loyalty, and lecture Lex about dealing with the Hardwicks. Mr. Luthor warns Lex about Victoria and the dangers of a relationship with her to the business. If he "sells out" his family, Lex will be alone in the world. Snoopy Victoria listens to the father-son conversation at the door.

What's up with Clark? Lana is organizing a blood drive. Clark offers help running it, since Whitney is out of the picture. Clark and Lana review the blood drive schedule on Lana's front porch. She thanks Clark for his help, and for always being there when she needs him. Clark comments on how Lana's aunt once dated his father. They are about to kiss, when Lana's Aunt Nell interrupts. Clark makes a date with Lana to watch the sunset from his loft the next day.

What's up with Whitney? He has been avoiding Lana all week and tells her he needs some space. Clark sees that Whitney has a Rx for heart medication in his bag. When he later confronts Whitney about it, Whitney tells Clark the medication is for his father, who is ill and undergoing tests in Metropolis all week. Clark reluctantly tells Whitney he should share this news with Lana, who'd understand better than anyone.

What will Clark do? Amy talks to Clark about Lex, and Clark realizes her obsession. Later at the Luthor mansion, Clark tells Lex about Victoria's snooping around on his computer, which Lex already knew about. Clark also tells Lex of Amy's obsession. Lex dismisses it as a teenage crush. When Lex asks about Lana, Clark tells him of the heart medication and Whitney. Lex knows of the drug, as his mother took it before her surgery and death. As Clark is leaving he hears a struggle upstairs. He races up to find Victoria, head underwater in the bathtub. The "invisible force" had tried to drown her. Clark pulls her from the tub, and she revives. As he does, the "invisible force" pushes Clark aside. With his x-ray vision, Clark sees the "invisible force" is human, cut by broken glass on the floor, leaving blood behind.

What's up with Chloe? Chloe and Clark discover green goo on the broken glass from the bathroom, that causes invisibility. They suspect Amy Palmer is involved, and Chloe offers to check her blood type from the blood drive against the blood found on the bathroom glass.

How it ends: At the Beanery, Clark tells Lex Whitney's father is sick. Lex says he should still pursue Lana, but knows he won't. Amy stops in to say hi, and Clark sees Lex's missing watch on her wrist. Lex and Clark go to see Amy's mom, inspect Amy's room, and finds a "Lex shrine" and his missing watch. Lex tells Mrs. Palmer Amy needs psychiatric help and offers to pay for it. He asks the family to leave the mansion that night.

Back at Clark's loft, Lana waits, watching the sunset. As they move closer, Clark tells Lana she needs to talk to Whitney. When she asks Clark "Why are you doing this?," Clark says he doesn't want to lose her friendship. They miss the sunset...and what else?

As Mr. and Mrs. Palmer and Amy are ready to leave, Amy tells Lex, "I just wanted to feel close to you." Brother Jeff is left behind to finish packing. As the Palmer's car pulls away, Lex, calling Victoria on his cell phone, has the phone thrown from his hand by the "invisible force."

Meanwhile Chloe comes to Clark with the blood tests. Although the sample from the broken glass does not match Amy's blood, Clark sees a match to Jeff, Amy's brother.

Clark rushes to the Luthor mansion, where he finds Lex tied up, being beaten by the invisible Jeff. Jeff has already taken a sword from the antique collection, and thrown it at Lex. He breaks another weapon against Clark's face and the wall. In the struggle with Clark, paint is knocked down from above, spilling on Jeff, as he's knocked out. Lex is OK as Jeff is taken away by rescue.

Back in his loft, as he looks at the moon through his telescope, Clark also sees Lana and Whitney embrace as he looks over to Lana's porch.