Doomsday

S11, E4: Sixteen-year-old Leo disappears just before a family trip to Greece, leaving his mother Melanie in shock. Believing she knew everything about her son, Melanie is stunned to discover he has secretly contacted his estranged father and become involved with a radical prepper group. As the team races to find him, Leo's hidden double life leads into a perilous world with life-threatening consequences.