Veteran firefighters from New York City, Chuck Levine, a notorious womanizer, and Larry Valentine, a widowed dad, carry the honor of their Brooklyn firehouse, Engine 506/Ladder 223. Their bond is tested when a collapsed floor during a building sweep nearly costs Chuck his life; after Larry saves him, Chuck pledges to repay the favor. However, when Larry attempts to adjust his life insurance policy post his wife Paula's passing, he learns that a paperwork oversight prevents him from designating his children, Eric and Tori, as beneficiaries.
In search of a solution, Larry finds motivation in a newspaper feature highlighting domestic partnerships. He approaches Chuck with an unusual request to enter into a civil union. Although initially wary, Chuck acknowledges his debt to Larry and consents, establishing a domestic partnership that allows Larry to name Chuck as his primary beneficiary. This newfound arrangement, however, draws scrutiny, and investigators suspect fraudulent motives, compelling the two to seek assistance from attorney Alex McDonough. To solidify their commitment, she suggests a formal wedding ceremony, leading them to Niagara Falls, Ontario, for a quick same-sex wedding, after which Chuck moves in with Larry and his kids.
Their journey takes an unexpected turn when they are invited to a benefit costume party, which ends in conflict with homophobic protesters. This incident thrusts their relationship into the public eye, leading to repercussions from fellow firefighters and Captain Phineas J. Tucker, who turns a blind eye to their troubles. They find an unexpected ally in Fred G. Duncan, a formidable firefighter who reveals his own struggles with sexuality.
Things become complicated for Chuck when he develops feelings for Alex. Their chemistry escalates during a vulnerable moment, yet Alex, believing Chuck to still be gay and committed to Larry, recoils, leading to tension between Chuck and Larry. Their friendship faces strain as they grapple with public perception and personal loss. Matters worsen when a petition circulates to oust them from the firehouse, prompting Larry to remind their comrades of the sacrifices he and Chuck have made for them.
As their fabricated relationship unfolds, they find themselves facing a court trial to prove its legitimacy. With Alex defending them, their fellow firefighters rally in support, recognizing the bond they share. The court proceedings take a wild turn when Fitzer, a city investigator, demands a kiss to prove their relationship. Just as they prepare, Captain Tucker comes forward, exposing their deception but also advocating for the importance of acceptance and understanding among others.
Following their release, the duo agrees to plead guilty to minor fraud charges. Fast forward two months, a joyous reunion occurs in Niagara Falls where Fred and Alex's brother, Kevin, celebrate their marriage at the same chapel that Chuck and Larry once visited. At the wedding reception, featuring musical guest Lance Bass, both Larry and Chuck explore new beginnings, embarking on fresh relationships while letting go of their past.
