On Beckett’s (Stana Katic) first day back on the job she and Castle (Nathan Fillion), with the still feuding Ryan (Seamus Dever) and Esposito (Jon Huertas), look into the murder of a local weather girl (Candice Mann) while attempting to hide their relationship from Gates (Penny Johnson), Lanie (Tamala Jones), and the other members of the precinct.
The investigation uncovers several suspects including another weather girl (Shannon Lucio) caught on tape having a fight with the victim the day of the murder, the basketball star (Kevin Daniels) who may or may not have been having an affair with the victim, and one of the reporters (Josh Randall) from the television station. They also discover the mysterious helicopter ride she took that forced her to take a trip to the emergency room a week before her murder.
More investigation uncovers the fact the weather girl was doing a little detective work of her own involving the dangerous airborne toxins from a carpeting factory located near the homes of several hospitalized children with asthma she befriended while doing charity work. Meanwhile, to keep up appearances that they’re both single, Castle agrees to a date with a talk show host (Jodi Lyn O’Keefe) which ends in an awkward moment for everyone involved, include Beckett who shows up with gun drawn believing her partner to be in danger.
Castle and Beckett’s first case as a couple has some fun moments including Castle playing Superman on the weather green screen, Lanie’s observation that Beckett is having regular sex, and Beckett’s reaction to finding a half-naked television star straddling Castle on his couch. I’m not sure how long the show can realistically keep the relationship secret from an entire precinct of cops, but for now it works.