Susan is in desperate need of help to figure out if Katherine was responsible for strangling her daughter, and the detective who agrees to help her, Denise Lapera (guest star Kathy Najimy), shares some history with her that they both would rather forget. In the meantime, Lynette learns about Julie's past affair with Nick Bolen, which leads her to have her own theory as to who may have strangled her. The Hodges are invited over for dinner by the Bolens, and Nick proposes to Bree that she hire Angie to work for her at the catering company. Meanwhile, Gabrielle takes advantage of her housekeeper (guest star Anna Katarina) by making her play the role of Juanita's tuitor.
Susan and Katherine are both sentenced to community service by picking up trash, and in the meantime Katherine finds a way to let Susan know she and Mike once had sex five times in a day, which annoys Susan, as her sexual ratio with Mike was never that high, leading her to believe he was closer to Katherine. Meanwhile, Gabrielle goes out of her way to get her daughter into Catholic school, and the only way to do so is by having Carlos send one of his employees, and Lynette's trainee, to Florida, much to Lynette's dismay, as she was training him to cover for her during her soon-to-come maternity leave. Angie refuses to make small talk with Julie Mayer, and Orson lets on that he is suspicious his wife might be cheating on him.
In the wake of another unexpected attack, Nick decides the time has come for him and his family to move away from Wisteria Lane. In the meantime, Susan and Bree clash over the latter's affair with Karl Mayer, whereas Gabrielle and Lynette clash over the latter's pregnancy. Meanwhile, Katherine's crazy schemes have brought Mike to a point where he can no longer put up with her, and a heated arguement between the two of them has shocking results.
Gabrielle and Lynette's friendship is on the brink of collapse, whereas Bree and Orson come to an agreement about their marriage. Meanwhile, Susan hatches a plan to help an irrational Katherine, and Danny's vital mistake might cost Angie her freedom. In the meantime, Christmas cheer is curtailed when disaster strikes, as a plane crashes down on Wisteria Lane, putting lives in peril.
In the aftermath of the plane crash, the residents of Wisteria Lane reflect on what their lives might have been had they made different choices: Susan contemplates a life with Karl had he not walked out on her, and Bree considers life without Orson. Lynette thinks about a future with her unborn twins, whereas Gabrielle imagines her daughter Celia aspiring to become a superstar actress, and Angie ponders the consequences should her secrets be revealed.
Susan turns up the heat for Mike, whereas Lynette discovers Tom's true intentions. Gabrielle is forced to examine feelings she's suppressed regarding her heritage, and Bree learns it'll be hard to undo the hurt she's caused Orson. In the meantime, Ana is more determined to land Danny.
Lynette balks at the idea of seeing a couples' therapist. In the meantime, Katherine shows no intention to moving back onto the lane, whereas Gabrielle and Susan are determined to find out which of their kids is in the smartest math group at school, whereas Orson makes life harder for Bree and Angie disapproves of Danny's new girlfriend.