Ben, Gwen, and Grandpa Max attend a family wedding for Max's nephew Joel and his bride-to-be, Camille. Before the day of the wedding, Ben tries to go swimming in the lake, only to interrupt a mud alien's attempt to sabotage the wedding. Ben defeats the sludge alien as Cannonbolt but finds the groom's parents pointing rifles at him soon after. He escapes with Gwen's help, and Max explains that the groom's side of the family are all Plumbers, while the bride's side are all mud-like aliens, called "Sludges", which the Plumbers were enemies with until Joel and Camille meet. This wedding represents a truce. During a dinner time with the families, they are confronted by Camille's ex-boyfriend. Ben tries fighting him with Diamondhead, but realizes the Sludge is immune to the diamond ammunition. As they fight, Diamondhead pushes Camille's ex-boyfriend into a hot tub, where he dissolves into the water. After this incident, Joel's parents try to convince Joel and Camille to cancel the wedding. They refuse, forbidding them to bring any Plumber gear and the wedding continues the next day. However, on the wedding day, chaos erupts when Camille's parents and ex-boyfriend revolt against the marriage. Max realizes that they just set up the ex-boyfriend plot so they could hide their own true color. The opposition shows their true selves and attempt to eradicate Joel. As Heatblast, Ben defeats them with a little help from Max, who bought some Plumber weapons, and the angry bride.
