The Kid Detective has done the best job, in recent memory, explaining why a mystery’s leading sleuth is such a sad sack.  The enigmatic and eccentric personality has become such a cliché in the genre, that the audience just expects and accepts the detective to be grizzled, or unhappy, or an unpredictable hot head.  In The Kid Detective, Abe Applebaum (Adam Brody) carries those traits, but writer/director Evan Morgan provides compelling motivation which fuels Brody’s top-form…