On a very special St. Patrick's Day, Stephanie Plum's grandmother, Grandma Mazur, sees a rainbow, finds a sack full of money-lots of money-and drags her granddaughter into another wild and wooly adventure.

Ex-jockey Snuggy O'Conner, aka Zigmond Kulakowski, likes his former mount Douglas Iron Man III a lot. So when Doug develops a sore leg, and his owner plans to retire him from the stud farm to the glue factory, Snuggy bundles Doug into a horse trailer, drives off with him and hijacks $890,000 from Trenton mobster Lou Delvina's headquarters to finance Doug's vet bill.

While Snuggy's giving Delvina's goons the slip, however, Grandma Mazur discovers the money. Convinced she has as much right to the swag as anyone else, she takes charge of it, buys herself a used RV and hires three-foot-tall computer geek Randy Briggs to drive her to Atlantic City, a town that really knows how to treat senior citizens.

Lickety-split, Stephanie (Lean Mean Thirteen) and her no-nonsense colleague Diesel catch up with her grandma. So do Delvina and his troops, who take charge of both Grandma Mazur and Doug - you can't have too many hostages - and set the stage for a hundred more swaps, quips and pratfalls. The frantic, anything-for-a-laugh jokes are brand new and nonstop.