We trained Oliver to be a service dog for a while—the type you take into schools and libraries where children practice reading The Very Hungry Caterpillar while tucked into his weird, hairless belly. But despite his talent for suffering sticky fingers, Oliver lacked the necessary motivation—preferring to be read to from the more borgeouis comfort of the couch.

Four years after we adopted Oliver, my husband suggested getting another dog. I hesitated. Yes, I wanted more dogs; after all, my life's dream is to have a farm spacious enough to take in senior rescues who will live out their waning days on cheeseburgers and green fields. Still, I felt an internal pulling of the reigns, some brief encounter with life's unspoken truths—you know, truths like ice cream tastes better in a cone, a house with children will rarely see a towel hung to dry, and that you can bet the new carpet you'll eventually need that the second dog you bring into your family will be an unholy mess.

I've seen this pattern before—a mathematical phenomenon in which the subsequent is equal to or greater than the sum of chaos in any pair of dogs. Second dogs are the ones who walk across the dining room table, helping themselves to the Thanksgiving turkey; the dogs who use drywall as teething wood and urinate on vegetable gardens. They are nocturnal barkers, incontinent as the moon shifts, the genetically unsavory descendants of werewolves, and dumb as they are sweet.

My sister's second dog greets every new arrival in a flurry of limbs and tongue—a fluffy, 70-pound bowling ball, and you are the last remaining pin. My neighbors spend every weekend patching up the fence that divides our property because their number two keeps finding her way into our yard and probably the dumpster of the local Pizza Hut.

The only trouble Oliver ever got his nose into was the butter on the counter, and really who could blame him?

As with most matters regarding happy tails and fluff, I ignored the peripheral warnings and adopted Luca, a scrawny mutt with a mysterious past. He came with minimal paperwork; names of possible breeds were crossed out and written over with new guesses at each vet appointment, only to land on "beats me?"

Luca's first and only attempt at formal training ended in a panic attack. He spent the entire hour howling and convulsing, desperate to get at the other puppies cowering under their human's folding chairs. I clung to him. "Take the stupid treat," I pleaded through tears and sweating salmon-scented palms.

"Do you want to put him in the closet?" the trainer, a sturdy woman specializing in bird dogs, asked. "Bad boys get the closet if they can't listen to instructions." I declined the timeout and held on like a rodeo cowboy for the rest of our time in class.

I was now in the territory where "dog crazy" goes from paw print tattoos to crying in the shower while fully dressed.

One day I asked a few of the kids to walk Luca to the park. I knew it was a terrible idea; children are no match for Luca's manic energy, but I needed a reprieve. Maybe he would break free and run away to some other adoring family a hundred miles away.

It only took about fifteen minutes for the kids to come back, beaten and bruised. "He's such a jerk," the oldest said. "I'm never walking him again." The younger two were coming up the walkway with Luca, wrangling him like a marlin on a fishing line. "He got away from us," one said. "Yeah, and he chased after this lady, and a dog in a bunny costume."

Luca had Houdinied his way out of the harness yet again, sprinting for the odd pair. In Luca's defense, their dog was dressed like a snack. "Get this animal away from me," the woman yelled as she and her bunny dog hightailed it out of the park—a sight I wish I had seen.

In the six months we've had Luca, I have aged like a U.S. president. A grey hair sprouted for every incident like the bunny dog, and I am dangerously close to looking like Helen Mirren.

I looked down at Luca; he was tangled in his leash, tired, but refusing to go down, like a toddler at bedtime. It was probably the best day of his life.

Luca is as loveable as he is bad. The kids are happy to relinquish their cheese sticks for sloppy kisses. My husband only occasionally threatens to return him to the bowels of hell from which he came.

As I type this, he is lying across my lap, trying to chew the charger to my computer. But I know it's not his fault. He is a second dog; unrelenting trouble is in his DNA.

But at least he never left me a dead mouse in my shoe like the cat does.