GLASGOW — HBO will premiere "Half Man," a six-episode limited series created by and starring Richard Gadd, on Thursday, April 23, at 9 p.m. The drama, an HBO/BBC co-production, is set in a working-class neighborhood of Glasgow, Scotland.

The series follows a toxic relationship between two pseudo stepbrothers, Niall Kennedy and Ruben Pallister, spanning decades. It explores themes of male sexuality, violence, anger, aggression, repression, shame, bravado and trauma.

Gadd portrays Ruben as an adult, with Stuart Campbell playing the character as a teenager. Jamie Bell plays the adult Niall, and Mitchell Robertson plays the teenage version. Neve McIntosh portrays Lori, Niall's mother.

In the opening scene, Ruben crashes Niall's wedding and punches him in a barn. The story then moves to 1986, when 15-year-old Niall, who is closeted and has a love of science fiction, is bullied at school for his physique and for his mother's relationship with a woman. Ruben, who spent two years in juvenile prison in the 1980s for biting someone's nose off, arrives at the school after his detention and shares a room with Niall.

Gadd wrote the first episode in 2019. "I sometimes just feel an impulse to write about something. I wrote the first episode back in 2019 and really wanted to go back to it, to honor the story and these characters," Gadd said.

Gadd, who also created and starred in "Baby Reindeer," had initially intended to take only a minor cameo role in the project. Bell suggested that Gadd should play Ruben. To take on the role, Gadd underwent a physical transformation, gaining muscle to achieve a burly physique.

Speaking about the title, Gadd declined to offer a definitive explanation. "I don't want to say why 'Half Man' because it's important for people to have different interpretations. I don't want to rob them of that," he said.