'Baby Reindeer' viewers watched a stalking drama — then hunted down 'the real Martha Scott.' A psychologist explains why true crime turns us into armchair detectives.

Netflix's "Baby Reindeer" gripped audiences with the story of Donny Dunn, an aspiring comedian who is stalked by a woman after he shows her a moment of kindness in the pub where he works. The series, which is based on the real-life experiences of its writer and lead actor, Richard Gadd, was met with …