For those whose sensibilities lean toward the darker side of human nature, Theatre in the Round Players has selected an ideal piece of holiday counterprogramming with And Then There Were None. One of the signature murder mysteries by Agatha Christie, grand dame of the genre, the play features all of the standards one might expect: an isolated location, a cast of morally dubious characters, a mysterious killer doling out death in increasingly imaginative fashion. More specifically, 10 strangers are brought to a deserted mansion on a remote island where they are each accused (via a recording) of harboring a dark secret. Soon after, the guests start turning up dead, murdered one by one in a manner paralleling an oft repeated nursery rhyme. It’s formulaic to be sure, but hard to complain when the ingredients are combined in such a delightfully macabre manner. Having regularly featured Christie works in previous seasons, Theatre in the Round Players undoubtedly understands the deft blend of suspense and humor that has continued to make these murder mysteries such perennial crowd-pleasers.