When she was a kid, Reckoning performer Holly Laurent wrote a short illustrated story about an imaginary town full of zombies.

Little did she know years later she would show off her nascent art skills to a charmed audience, spin out the yarn on stage, and use it as the basis for a long-form improvised comedy sequence. Last week she did just that at iO Theater in Chicago as part of the Reckoning’s regular Tuesday night slot.

Holly’s book of horrors was part of Show and Tell, a structured performance that’s a twist on the old improvise-around-an-object shtick.

“We switch ideas every couple of weeks or from month to month,” says team member Jake Schneider. “We use unfinished written works, read a friend’s poetry, or something from the news we’re interested in. It’s always something new that appeals to our aesthetic.”

The Reckoning, iO’s longest-running improv-based group, is best known for its supreme mastery of the Harold. That’s the carefully structured kind of long-form improve that creates symmetry and resonance in a free form stream of gags.

Sounds technical. Yet the Reckoning’s adept at keeping its well-worn form of comedy intelligent and apparently effortless, finding the truth in the humor and keeping the audience constantly involved.

“Another thing we sometimes do is bring people up on stage and talk to them,” Schneider says. “We use that as the basis for a scene.”

Whether the jokes come easily or they have to be developed, the group sticks to its impromptu premise.

Spontaneity like this takes hours of intense preparation. Team members don’t know how each night will develop, but they meet twice a week to hone their comedic skills. They’re constantly developing their acting chops as well.

When they’re not rocking out with the Reckoning, the performers lead diverse lives. For example, Pat O’Brien and Brad Morris are part of Second City’s Mainstage ensemble. Holly Laurent and Jet Eveleth have their own two-woman show, I Live Next Door to Horses. Charlie McCrackin writes, and Beau Golwitzer is earning a masters degree in writing down in Florida.

“This diversity makes our performances all the more rich,” Schneider says. “We all come from different places, but for one reason or another we’ve become very committed to this opportunity.”

The cast’s commitment is evident, but rarely has a comedy group been so proficient at making things up as they go along.

Take their lack of a leader.

“There’s no one with a set itinerary,” Schneider says. “At some point, someone offers to do something. They’ll say they’re interested in a festival or workshop, so we’ll go off and do that. It just kind of happens.”

So what keeps this motley bunch together?

For Schneider, it’s a sense of fun and their expertise.

“They’re interesting to play with. Everyone in the Reckoning is the best at what they do in Chicago.”

Now they’re bringing that expertise to Theatre 99, promising their carefully planned brand of material made up on the spot.