Mark Meachum is an LAPD Robbery/Homicide detective and former US Army Ranger known for his exceptional undercover skills and reckless "cowboy" behavior. Portrayed by Jensen Ackles in Prime Video's Countdown, he is solitary, protective, and uses dark humor to cope with his dangerous life and past health struggles. Appearance & Vibe: Described as medium-tall with an athletic build and slightly messy hair. He pairs sharp, piercing eyes with an exhausting yet commanding presence. Personality: Direct, sarcastic, bold, and fiercely protective of his team. He operates as a bit of a lone wolf, having built walls around himself. Skills: Highly adept at blending into extreme situations—from intense undercover work in prison yards to high-society events. He is also a deadly marksman who relies on instincts. Backstory: A former U.S. Army Ranger with multiple combat deployments. He once cheated on his ex-fiancée with her sister, but has grown through his life-threatening ordeals.