mystery story vs mystery

mystery story and mystery both are nouns.

Word	Noun	Adjective	Verb	Adverb
mystery story	Yes	No	No	No
mystery	Yes	No	No	No

As nouns, mystery story and mystery are synonyms defined as:

mystery story and mystery: a story about a crime (usually murder) presented as a novel or play or movie

Other synonyms of mystery story include whodunit.

mystery story (noun)	mystery (noun)
a story about a crime (usually murder) presented as a novel or play or movie	something that baffles understanding and cannot be explained
	a story about a crime (usually murder) presented as a novel or play or movie