A mysterious woman arrives in Smallville, claiming to be Clark's birth mother. The Kents tell Clark what happened the day they found him, how his adoption was fixed, and why Jonathan hates the Luthors. Guest-star Blair Brown portrays "Rachel Dunlevy." Ms. Brown has appeared in several films and starred in the TV series "The Days and Nights of Molly Dodd."

Who is Rachel Dunlevy? A woman ambushes Clark at school, introducing herself as his birth mother. The Kents deny it. Rachel tells Lex she gave up a baby for adoption years ago, and she thinks he's Clark. Rachel claims the boy was Lionel's illegitimate son, so the boy is Lex's brother. Rachel confronts Lionel with her claims. Rachel was Lex's mother's nurse during her illness. She had 7 years of psychiatric care after her son "Lucas" was taken away by Lionel.

What's up with Chloe? Clark angrily accuses Chloe of snooping into his adoption and privacy, after he asked her not to. She admits she posted some info on some adoption Web sites. Rachel contacted Chloe. In their conflict, Clark makes a hurtful comment about Chloe's own absent mom. We learn her mom left her dad when she was 5-years-old.

The story of Clark's adoption: Clark asks Martha and Jonathan about his adoption. Jonathan does a flashback to tell the story of the Great Meteor Shower of 1989. They found Clark and the spaceship as they tried to get home safely. Martha wrapped Clark up and into the truck, Jonathan hid the spaceship in the back of his pickup. Lionel Luthor flagged them down on a country road for help with 9-year-old Lex, who was unconscious in a field. Jonathan took Lionel and Lex to the hospital. Lionel credited Jonathan with saving Lex's life, and offered his help if ever needed. Later, the sheriff came to the Kent home, checking on their safety. He saw Clark, and asked who he was. On the spot, Martha made up a story that they had just adopted him, named him Clark after her family name, and brought him home from Metropolis. Jonathan asked for Lionel's help in making the "adoption" legal.

What's up with Clark? Now the sheriff comes to the farm, telling the Kents that Rachel has gained a judge's order for a DNA sample from Clark to prove her relationship. He gives the sample, but later breaks into the genetics lab with Pete, switching the DNA sample with Pete's saliva.

What's up with Lana? Lana is digging into her own origins. She discovers the man in the photo with her mother is Henry Small, of the founding family of Smallville. She visits his home. Lana asks Henry if he loved her mother, and if he's her father. Henry is married with his own family, and tells Lana she is mistaken. Later Henry admits he doesn't know if Lana is his daughter, but is willing to find out.

What's up with Jonathan? Clark asks Jonathan why he hates Lionel Luthor if he helped in the adoption. Jonathan explains that the day Lionel brought Jonathan the legal adoption papers, Lionel asked Jonathan to speak to his friends the Ross brothers (Pete's family) to persuade them to sell Luthor their farm. When Jonathan refused, Lionel gave him a masked threat about revealing the adoption. Jonathan did speak to the Ross family, and now carries the guilt of feeling responsible for the growth of LuthorCorp. and the ruination of the community, as he helped Lionel gain a foothold by using his influence. What's up with Lex? Lex asks Clark about Rachel's claim that they may be brothers. Clark tells him its impossible, since she is not his mother. To get the truth from Lionel, Rachel surprises Lex with an injection to knock him out, kidnapping and imprisoning Lex in her home. She wants a press conference with an announcement from Lionel stating Clark is their illegitimate son. Lionel does hold a press conference, announcing he will never give in to the extortion of the kidnapper. Enraged, Rachel swings an ax towards Lex. He pushes her away, and falls hitting his head and slipping into unconsciousness.

How it ends: Clark arrives at Rachel's house as Rachel is about to swing the ax at Lex again. He stops her, and she falls to the floor, sobbing in a breakdown. Later at the mansion, Lex asks Lionel about Rachel's claims. Lionel admits he was unfaithful to Lex's mother. He says Rachel showed up with an infant, accusing him of paternity. Lionel saw to it that the boy was placed with a suitable family, and paid off Rachel, getting her into psychiatric treatment. Lionel says the boy "Lucas" died before his first birthday. After Lex leaves the room, Lionel opens a locket in which he keeps a photo of himself with a blonde boy, aged 5 or so. The locket also contains a lock of blonde hair.