Much to Jessie's horror, Billy fell in with the wrong crowd and was desperate to impress his new friends. During a night out following their exams, a man named Evan Norwood was viciously beaten and left for dead by Billy and his friends. Under Joint Enterprise laws, Billy was sentenced to three years imprisonment for the assault along with his friends, Luke Dockley, Nathan Delfield, and Freddie Hart. Jessie was convinced of her son's innocence, although Ellis, whose relationship with Billy had fallen apart as Billy refused to stop his friends bullying Ellis, was just as convinced of his brother's guilt.
In September 2018, Jessie revealed Billy would be granted early release from prison later in the year. In November 2018, Billy was hospitalised after a fight with another inmate, who was also hospitalised.
On Christmas Day 2018, Billy turned up at Jessie's wedding to Marlon Dingle, having been released from prison. Jessie was elated to see her son and proclaimed the day was "perfect". The joy quickly faded away when Marlon's first cousin once removed, Aaron Dingle, attacked Billy. Aaron had previously mentioned to his husband Robert Sugden that Billy was part of the prison gang that made his short prison sentence almost two years ago a living hell.