Episode recap from the website:
Gaby stuns her friends by telling them she's back together with Carlos -- and that they're leaving town to escape Victor, since he knows about their affair and is being released from the hospital tomorrow.
While they're saying their goodbyes, Karen McCluskey alerts them that a tornado is on its way. Lynette asks Karen if the seven Scavos can stay in her basement. and she reluctantly agrees.
Bree stops by to lend Susan some hurricane supplies and Susan says maybe it's time to tell Orson about Mike's addiction problem. Bree admits she'd already told Orson last week. Susan is upset, but doesn't let on why.
Susan confronts Orson, even though he's with a patient. She wants to know why he gave Mike the pills when he knew he had a drug problem. Orson claims he thought he was helping.
Mike finds a note from Susan that says "See me," instead of the pills in his secret stash. As they argue, he pulls at her arm, causing her to fall down the stairs. He rushes her to the hospital, insisting she be seen immediately since she's pregnant, but the staff is swamped and tells them they have to wait. Mike gets impatient and punches out a hospital staffer. Security is called and Mike is restrained until after Susan is examined and released. The baby's fine and she's only suffered a mild sprain. Mike apologizes and Susan tells him she talked to the doctor about a rehab facility. Mike swears he can kick this by himself but she firmly tells him no, he will go to rehab now or she will leave him. Mike gives in to her wishes.
Katherine is alarmed to see Sylvia, Adam's stalker, outside her house. They argue and Sylvia insinuates that Adam was happy to see her when she stopped by yesterday: Didn't Adam tell her? Katherine spits in Sylvia's face in full view of Bree, who invites Sylvia in for tea.
Sylvia tells Bree that Adam is in love with her, not Katherine. As proof they were lovers, she mentions Adam's snake tattoo on his shoulder. Bree tries to get her to leave and Sylvia barricades herself in the bathroom where Bree planned to ride out the tornado.
A neighborhood boy informs Edie that Gaby and Carlos are moving. While she's on Gaby's porch, a courier shows up with the paperwork for the Cayman Islands account that Carlos asked for. Mistaking her for Gabrielle, he hands Edie the papers, which gives her everything she needs to access the funds. Gabrielle sees Edie with the file and runs after her.
Adam apologizes for not warning Katherine that Sylvia had shown up again. Bree asks for Adam to come help lure Sylvia out of their bedroom. She refuses when she hears that Katherine is also there. While Adam tries to reason with her, Katherine assures Bree that what Sylvia said is a lie: There was no affair, only one kiss Adam gave her out of pity, which led to an accusation of sexual assault. Katherine wanted to fight the claim but Adam didn't want to lose his license. Bree says she would have spit in Sylvia's face too.
Lynette wants Karen to kick Ida's cat out of the basement because Tom is extremely allergic, but Karen takes Ida's side. Tom's having trouble breathing so Lynette smuggles the cat upstairs. Karen catches her and Lynette wants to know how she can choose a cat over Tom, especially after all their years of friendship. Karen insists they're not friends since Lynette never asks her over unless she wants something. The door blows open and the cat runs out, so Karen runs after him and Lynette tries to get her back inside. Karen only agrees when sees the ominous funnel cloud at the end of the street. They rush into the bathroom and hide in the tub under a mattress.
Gabrielle breaks a window to get into Edie's place so she can get the file back. Edie says she'll leave them be -- for 60 percent. Gabrielle tackles her and runs outside with the file. As they fight over it, the winds blow the papers out of their hands. Edie looks up in terror as the cyclone approaches and hustles Gabrielle back into the house. Gabrielle reluctantly agrees to hide in Edie's crawl space with her. She tells Edie she's sorry that Carlos and she lied to her. Edie says they're both going to get out of here okay and she's going to go on hating her for years to come. But then she admits she doesn't really hate Gabrielle, just that she fell hard for Carlos, which was stupid since she always knew that he'd go back to Gabrielle. They hear a huge bang and hug each other tight.
Sylvia still refuses to come out so Orson hustles them all into a closet. Trapped in the small room, Katherine and Bree blame each other for their predicament. Katherine apologizes, saying she's tense because of Sylvia. Bree commiserates, relating Sylvia's "insane" ramblings, including the detail about Adam's snake tattoo. Katherine says that Adam used to have such a tattoo, but he had it removed. Katherine coldly asks Adam if that's why they settled the lawsuit and lost everything. Adam tries to explain, but she won't let him. Bree reaches out and squeezes her hand in sympathy.
Carlos rushes to Gaby's house and finds Victor sitting in the living room with a gun. He tells him they're going to wait for Gaby, together. Carlos tries to convince him that he and Gaby hadn't planned to get back together and never meant to hurt him. Victor's response is to start shooting. Carlos runs outside and Victor follows, gun in hand. They struggle for the gun and it falls into the street -- where an airborne car falls on it. Stray objects fly through the air as the two men fight. Carlos knocks Victor out and is trying to get inside the nearest building when Victor comes after him with a lead pipe. Suddenly Victor stops short -- he's been impaled by a flying fence post!
Sylvia finally emerges from the bathroom, giving Adam one last chance to come with her. When he doesn't answer, she opens the front door and promptly gets sucked up by the tornado.
Finally all is quiet on Wisteria Lane. Bree is shocked to find her house has been badly damaged, but Lynette screams in horror when she sees that hers has been completely destroyed.
Edit: That last paragraph - Lynette screams because the house destroyed is Mrs McCluskey's - ie. where her family is hiding out in the basement. There's just a huge pile of debris.