Of all the crazy storylines on the Netflix docuseries, "Tiger King," none are more captivating than what happened to Carole Baskin's husband ... and law enforcement's asking for help in cracking the case.

Hillsborough County Sheriff Chad Chronister says the disappearance of Jack "Don" Lewis -- Baskin's hubby who was last seen on August 18, 1997 -- is still an active cold case ... and he's hoping "Tiger King" fans can help him solve it.

The Tampa-area sheriff says with all the attention surrounding Don's case ... "I figured it was time to use the popularity of the show to see if anyone wanted to come forward with new leads."

For those who don't know ... Lewis was declared legally dead 5 years after his disappearance, but nobody has ever been charged in his death or has any clue of his whereabouts.

People have theories, though ... especially "Tiger King" star and Baskin's #1 enemy, Joe Exotic, who believes she killed her husband and possibly fed him to her tigers. Baskin has denied having anything to do with Don's disappearance or death.