I'm a risk analyst for a major insurance firm, so when my wife and I were planning a birthday party for our seven-year-old, Crispin, my mind naturally turned to liabilities. We'd settled on the theme of a "backyard carnival", complete with a swing set, a trampoline, merry-go-round, and a giant Slip `n Slide. So I carefully inspected the equipment for safety. It all seemed sound.

We have a home on a bluff overlooking the ocean. As it happened, on the day of the party our neighbors were trimming their fichus trees. We heard the sound of their wood chipper buzzing occasionally from the other side of our tall hedge. It was a little irritating, but not disruptive.

The party started off wonderfully. A clown we'd hired made balloon animals, Crispin eagerly opened his presents, and all the children enjoyed cake and fruit punch. The weather was mild, the skies clear. It seemed a perfect day.

Then we brought out the Slip `n Slide.

The problem with water slides is what we in the trade call "distributed water deficiency zones", or in layman's terms, dry spots. If a child hits one of these, it can put the brakes on the fun, and send them sliding down a path of medical claims--contusions, concussions, lacerations, abrasions, whiplash, back rash, and disc impaction. And that's just for starters. From there, it's a slippery slope toward major litigation.

To avoid even the remote possibility of such injuries, I invested in this 55 gallon drum of water soluble personal lubricant--the idea being that the children could enjoy the slide in complete safety, then wash off in the hose before their parents came to retrieve them. With that in mind, I dipped each child into the vat before allowing them to cue up for the slide.

The Slip `n Slide itself performed admirably, as did the lubricant. That, in fact, was the problem. Due to the slight downhill gradient of our yard, the children built up so much speed that they skidded across the lawn and into a retaining wall at the other end of our property, with sufficient force that I had to put an end to the activity.

I endeavored to roll up the mat--no easy task, as the lawn surrounding the slide was itself now lubricated, and I struggled to maintain my footing. When I looked up from my labor, I grasped for the first time the scope of the liabilities I had unleashed--a horde of extremely well-lubricated seven-year-olds, hyped up on sugar and desperate for fun.

I saw young Eliza Gimmelman climb onto the trampoline. She began jumping, but the pad soon became so slick that she lost all control. Her wild flailing unfortunately fell into harmonic synchronization with the motion of the springs, propelling her ever higher, until she soared above the trampoline's safety enclosure, over the hedge and into the neighbor's yard. There came a ghastly grinding sound, and I could tell from the crimson plume that followed, it would be a total loss.

Twins Jeremy and Mason Lafferty were on the swing set. Having attained the swings' full range of motion, they were apparently having difficulty holding on. At that point, the swings became human catapults. Mason separated on the backswing, arcing over the roof of our home toward the street beyond. I surmised from the screeching tires, car horns and screams of horror that he was also unrecoverable. A terrified Jeremy soon lost his grip as well, sailing forward over the bluff, and plummeting 300 feet down into the ice-cold, shark-infested waters of the San Francisco Bay. An open claim, but not promising.

The rest of the children were clinging to the merry-go-round. Having just witnessed the violent deaths of at least two of their playmates, they were no longer in the mood for fun. However, the lubricant had dripped from their glistening bodies into the central cog, allowing it to spin far faster than it was designed to, and this, likely combined with other factors--their relative weight distribution, the slight incline of the ground--caused their motion to become self-sustaining, and the centrifugal force built upon itself until they became a blurry, screaming disk of human suffering. Then they began to fly off like cannon balls.

Martin Duckworth was the first to go, causing significant structural damage to our greenhouse. Lisa Aurelio shattered a line of ceramic garden gnomes, and Ethan Green slammed into our Audi Q7 so hard it had to be written off--as, tragically, did he. Several other children left what looked like gingerbread man indentations in the siding of our home. It was terrifying.

When the wheel finally came to a stop, there was only one child aboard. As luck would have it, it was our own beloved Crispin, huddled in the center of the merry-go-round, weeping. My wife ran to him and hugged him with all the might of a relieved, traumatized parent. A little too hard, as it turned out. Lubricated as he was, he shot from her arms like a wet bar of soap, up fifteen feet in the air, landed on the trampoline, and then soared, in a half-gainer, over the hedge, into the wood chipper.

Since then, I've asked myself a thousand times, is there anything I could have done differently? But in the end, no actuary table could have predicted this bloodbath. I can only conclude that this was an act of God. And that, to me, is truly terrifying. Because we're not covered for that.