Clark loses control and injures a college student who almost assaulted Lana; Helen's ex-boyfriend returns to try and win her back.

What's up with Lana? Three college frat boys threaten Lana at closing time at the coffee shop. Clark arrives in time, confronting the guys outside, telling them to stay away. When they insult Lana, Clark fights them off, throwing frat boy Andy into the windshield of the Sheriff's patrol car. The tough new female Sheriff Nancy Adams questions Lana, Clark, Jonathan and Martha. Sheriff Adams wants Clark to do community service as punishment. She tells Lana her case won't hold up in court. Lana's thankful that Clark saved her, but feels violated and wishes she could've saved herself. Lex offers to teach her self-defense, instructing her to channel her anger.

What's up with Clark? Frat boy Andy's family is suing the Kent family for $1 million for Andy's injuries. While getting teased for his community service job of picking up trash, Clark sees Andy on the street. He asks Andy to leave the Kents out of the lawsuit. Using his X-ray vision, Clark sees Andy is faking his injuries, as Andy removes his neck brace once inside his friend's van.

What's up with Helen? Lex's girlfriend Dr. Helen Bryce is feeling a bit neglected when Lex stands her up for another date. The next day at the hospital, Helen is surprised by former Med school boyfriend Paul. He says he had business in town, and read she was to be married. He dropped by to give her flowers and say hello. Lex shows up. Helen gets beeped. Alone with Lex, Paul tells Lex to hang onto Helen, if he can.

Later that night in the hospital parking lot, Helen's car won't start. She calls Lex and waits for him to pick her up. Paul surprises her again. Lex arrives and jokingly suggests Paul may be stalking Helen. He asks Paul to stay away. Paul doesn't like Lex's threatening tone. Lex has Paul followed.

Guest-star Anson Mount portrays Paul Hayden. Anson has made TV appearances in "Ally McBeal," "Sex in the City" and "Third Watch." Film roles include parts in "Boiler Room," "The Truth About Tully," "Urban Legends: Final Cut," "City by the Sea" and "Crossroads" with Britney Spears.

Who is Paul Hayden? When Paul is alone in his motel room, we see that Lex was right in his judgment of the desperate stalker. Paul cuts his own face by smashing his forehead into a mirror. Bruised and cut at the hospital, Paul tells Helen that Lex had him beaten. Sheriff Adams takes Paul's statement. Helen tells Lex of Paul's accusations. She also tells Lex that one of Paul's ex-girlfriends had been abused by him and warned Helen, causing her to break up with Paul.

Later Paul surprises Helen in the empty Pathology Lab. He gets aggressive, in a jealous rage. She tries to run. Lex calls Helen on the cell phone, witnessing the struggle between the two as he races to the hospital. Lex finds Helen unconscious, stabbed and bloody on the lab floor.

What's up with Lex? While Helen is undergoing surgery, Sheriff Adams has set up roadblocks to catch Paul. She's waiting for a warrant to search Paul's motel room. She tells Lex not to tamper in the investigation. Lex races off in a fury. Lex searches the motel room himself. Clark goes in after Lex. They find the body of Lex's security guard, who was trailing Paul. Lex traces the guard's car to the train station, knowing Paul used it to get away. Lex spots Paul in the crowd, then catches him at gunpoint. Paul kicks Lex and runs. Lex chases him down. Clark is also searching. Paul and Lex fight in a train car. Paul gets the advantage long enough to raise on ax to attack Lex. Using his X-ray vision, Clark sees the attack in progress, and bumps the train car to knock the ax away. Lex gains the advantage, pointing the gun at Paul's face, but then pistol whips him in the head to knock him out. Sheriff Adams finds Lex and Clark over Paul. She warns them to stay out of police work. Lex says he made a citizen's arrest.

How it ends: At the Talon, Lana asks Andy to drop the lawsuit. She says she knows he's faking injuries. He comes towards her, making a pass. She uses her new talents in self-defense and beats him up. Andy drops the lawsuit, lifting Clark's worry of being sued.

At the mansion, Lex tells Helen that Paul is pleading temporary insanity. Lex tells his attorneys not to fight it, Paul needs help. Lex confesses to Helen that she's the one who saved him from killing Paul. Lex gives her a ring and proposes to Helen. They kiss.