What's so thrilling about an unsolved murder case? A lot, I say!

After about 20 years, the high-profile Martin Tankleff murder case has drawn to an end. Tankleff is a free man, no one else has been charged with the crime, yet he hasn't been fully exonerated by the state. End of story?

If you still feel unsettled, you're not the only one. To some, the overturning of his conviction is a just conclusion to the case; others read it as a twist in a bigger mystery.

Arie Kruglanski, a professor of psychology at the University of Maryland, has uncovered psychological underpinnings in the tension people feel over unsolved crimes and other disturbing uncertainties in life: it's all driven by a fundamental "need for closure."

A desire to have a clear conclusion to any story is natural, Kruglanski says. Whether you're anxiously turning the pages of a detective novel or mulling over the conspiracy theories that have kept the Kennedy assassination alive for decades.

To Sarah Weinman, a writer, critic and blogger specializing in crime fiction, the public fascination with the Tankleff case resonates with the magnetism of a good mystery novel. "As long as something is unresolved, there's still the potential for resolution. There's still suspense," she says. "Suspense is a very powerful, very provocative emotion or feeling."

But we vary in our desire for conclusiveness. "Some people, because of their temperament or because of the way they were brought up, find uncertainty more unpleasant than other people," says Kruglanski. That could play out in their social interactions and politics as well--in ways that society may view as positive or negative.