Windfall is a serial drama television series about a group of people in an unnamed small city who win almost $400,000,000 in a lottery.
A group of 20 friends and acquaintances gets together for their regular once-a-month lottery party in the neighborhood. The following morning they each find themselves $20 million richer -- except for one participant who forgot to sign the list. Cameron gets a visit from an old student with odd demands, Damien finds a way to help a girl in need while helping himself, and Sean needs a way to collect the money without revealing who he really is.
A spontaneous shopping spree in Paris gives Beth and Nina time to spend time with each other without their husbands. Damien throws a big party and Frankie discovers that she's having romantic feelings for him. Zoe helps Sean in devising a plan to get a hold of the money - and to get away from his dangerous past. Kimberly discovers that her son Ethan's school needs help. Finally, a new character comes forth demanding a share of the winnings.
Sunny's claim for a share of the money freezes everyone's winnings, and Nina and Peter find themselves on opposite sides of the battle. Cameron's decision to take care of the baby without consulting Beth puts a strain on their marriage but a near-tragedy makes Beth change her mind. When it looks like Zoe might have skipped town with Sean's money, he finds a surprising - but reluctant - ally in her sister, Tally.
The news on Zoe's disappearance raise the alert level in every house. Sean continues the search for Zoe with the help of her sister, Tally. Cameron and Nina feel drawn together, but they must resist the urge and keep their marriages afloat. The Scaefers decide to get a new house but when a new neighbor invites Peter on an exclusive trip to Mexico, Nina is left alone to deal with the escrow. Frankie feels out of place when her mother takes her to New York, but she is pleasantly surprised to see a familiar face there.
With Zoe still missing, Sean decides to hire a private investigator who quickly finds some promising leads. Returning home from New York, Frankie finds out that her father has been involved in a shooting and is taken in custody. Peter tries to find investors for the bicycle factory by throwing an extravagant party at their new mansion. Meanwhile, Nina and the girls take care of the injured Sunny, and Damien finds himself torn between two women.
The tragedy of losing Zoe brings Sean and Tally closer together, but things soon get complicated when they learn that Tally will inherit her sister's possessions - including Sean's winnings. Peter is forced to look for a new investor when he clashes with some of the partners over how to run the bicycle factory. Cameron confesses a past mistake to Beth, leaving her wonder whether their marriage is worth saving. Meanwhile, Frankie hangs out with her bodyguard in New York, and with Galina still in custody, Damien snoops around in her stuff looking for clues about her dishonesty.
Peter and his new investor Sunny fly off to Europe to sign a big advertising deal for the bicycle factory. When one of their daughters is taken to hospital, Nina is left alone to struggle with two restless kids but she finds comfort in Cameron. Damien must find a way to prevent Galina from getting deported once their divorce is finalized. Meanwhile, Tally and Sean notice that huge sums of money are missing from Zoe's account.
Peter and Sunny throw a party to celebrate the unveiling of the company's new bicycle model. Cameron and Nina look for comfort in each other after being treated coldly by their spouses. While Damien moves back home, Frankie tries to desperate convince her mother to move away from New York. Meanwhile, Sean and Tally are still looking for the truth about Zoe's disappearance, and Beth bumps into Kimberly who gives her some valuable advice.
Hardships at the office bring Peter and Sunny closer together when they must deal with the allegations that a biker sponsored by the company has been using illegal drugs. Nina's attraction to Cameron is distracting her ability to make preparations for the kids' school play. Damien and Frankie go on a road trip, and Beth meets a French chef at Maggie's restaurant. Meanwhile, Sean is still looking for clues about Zoe while Tally is ready to give up the search.
Sean runs from the law after he and Tally are questioned in connection with Zoe's death. While Nina and Cameron plan for a future together, Peter forces his protégé Colin Evett to make a life-and-death decision about his career. Beth looks into adoption options, and Damien presses Galina to sign the divorce papers.
After Nina and Cameron's affair is revealed, Peter finds himself looking for comfort in Sunny. Sean presses the truth out of Tally. Maggie throws an engagement party for her brother Ramon and his gorgeous fiancée but gets suspicious about her motives for marriage. Damien continues to push forward his divorce from Galina but agrees to help her when he finds she's gotten herself in trouble with a married man.
After their night together, Sunny feels close to Peter and reveals a secret. News about their parents' separation hits the Schaefer girls harder than expected. While Damien and Galina try to work out what to do with the baby, Frankie makes a new friend in the hotel owner's cute son. Meanwhile, Sean seeks Maggie's help after being shot, and she agrees to help him in finding incriminating evidence about Tally.
In the series finale, Peter makes a decision about his marriage. Beth receives good news from China, and Cameron begs her for a second chance. Damien finally makes a choice between Galina and Frankie. Frankie, however, gets disturbing news about her father. Sean is released from custody, but Tally not coming clean about Zoe's death creates tension in their relationship. Meanwhile, Kimberly throws her son a birthday party – with some surprising guests.
