WordNet (r) 3.0 (2006):

whodunit
    n 1: a story about a crime (usually murder) presented as a novel
         or play or movie [syn: mystery, mystery story,
         whodunit]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "whodunit":
   Marchen, Western, Western story, Westerner, adventure story,
   allegory, apologue, bedtime story, detective story, fable, fabliau,
   fairy tale, fantasy, fiction, folk story, folktale, gest,
   ghost story, horse opera, legend, love story, mystery,
   mystery story, myth, mythology, mythos, nursery tale, parable,
   romance, science fiction, shocker, space fiction, space opera,
   suspense story, thriller, work of fiction