Tread Perilously returns to the modern era of Doctor Who with the Christopher Eccleston story "Boom Town" and find a member of the family Slitheen waiting for them.
As the TARDIS makes a stop-off to refuel in Cardiff, Mickey comes to visit Rose and feel inadequate in the presence of Captain Jack Harkness. But the frivolity is dampened when the Doctor discovers Margaret, the lone Slitheen to escape destruction in London, is now the Lord Mayor. The group apprehend her and plan to take her to Raxacoricofallapatorius to face her sentence. With the engines still recharging, the group spend a long night facing certain truths.
Except for Captain Jack. He's too busy connecting the TARDIS to a surf board.
Justin tried to overcome his hatred of Billie Piper and fails. Erik finds he can almost pronounce Raxacoricofallapatorius without a lot of effort. The pair discuss Eccleston's progress as the Doctor from the lows of "Aliens of London" and the damn shame that he didn't stay on another year. Justin suggests he needed a different companion. The pair also go on tangents about Ant-Man, Sam Wilson's suitability as Captain America's boyfriend and the entitlement of Kylo Ren. Erik also recalls the time John Barrowman wouldn't stop touching him.