She was meant to be a companion for our cat Dizzy. She looked identical.  The same kohl-rimmed eyes. The same silky, silver fur. The same sweet face. She was Dizzy’s Doppelganger.

But inside?

A heart of darkness.

Dizzy, our Maine Coon cat, was a year old when I began to wonder if she might be lonely. “What do you think she does all day when no one is around?”

“She’s a cat,” my husband Marc said. “She’s fine.”

“She needs a friend,” I insisted. We adored Dizzy. Her charming chirps and trills. Her languorous looks. People always remarked on her beauty. “Let’s get another one who looks just like her.”

“If you’re looking for a lap cat, this one’s a honey,” said Mrs. Klase, Dizzy’s breeder, days later.  She placed a tiny tortoise shell tabby in my arms. “I call her Funny Face.” One side of her face was the color of cream; the other, chocolate. A yin-yang cat.  She nestled against me and purred loudly.

“She is sweet,” I agreed. “But do you have any silver ones like Dizzy?”

She did. A seraglio of long haired kittens, all looking as if they were wearing furry harem pants. Jonathan played with Funny Face while Mrs. Klase fetched a silver brother/sister pair.

“I want this one, Mom,” Jonathan said, an iron grip on Funny Face.

But I couldn’t let go of the idea.

“How would you like to take home two?”

His grin was huge. “Really?”

We spent twenty minutes playing with the silver siblings. The boy was friendly and adventuresome. His sister wasn’t.

“Take the girl. I don’t want a male cat,” Marc whispered.

“Why not?”

“I can’t stand the thought of having to get him ‘fixed.’”

“Are you serious?”

He crossed his legs.

“What can you tell me about her personality?” I asked.  Mrs. Klase shrugged, noncommital.

We drove home with two kittens. Funny Face, whom we immediately renamed Fudge, and the silver girl we decided to call Daffy. “Like Dizzy and Daffy Dean,” said my husband, the baseball historian.

But Daffy was not a team player.

Dizzy loathed her immediately. She leapt to the back of the sofa and glared, as if to say, what’s this bimbo doing here?

Fudge slunk away; Daffy stood her ground, growling. After much hissing and swatting,  they reached a clawed truce.

She was testy as a teenager, and as schizoid as Sybil. One moment she’d play the cat coquette, all fun and flirty, inviting you to play. Then she’d rear back, grooming her fur frantically as if to erase any trace of human scent.  She’d get high licking the glue off packing tape; she’d  roll around ecstatically on top of a damp peppermint teabag.  If you called her name, she’d stare impassively. Gorgeous but vacuous. The Paris Hilton of cats.

“Does she seem a little off to you?” I asked Marc.

A year later, when we visited the Cat Show, Mrs. Klase was selling two smokey grey kittens. Jonathan reached for the feather tickler.

“Don’t fall in love,” I warned.

“Too late, Mom,” he said.

That’s how Moxie came home with us.

Daffy was not amused.  She expressed her displeasure by leaving little piles of poop in odd places. Beside the basement door. Beneath the playroom window. Behind the litter box. She was sneaky; we never saw her do it. We bought new litter boxes. Different brands of litter. Nothing helped.

But Daffy had a champion: Shana, the behavioral therapist who works with our autistic son Mickey.

“I adore her!” Shana gushed.  “All your cats are beautiful, but this one is Miss America. I’d take her in a heartbeat.”  She squeezed Daffy, who squawked crossly. “Does that sound shallow?”

“It’s a mistake to pick pets for their looks,” I said. The rueful voice of experience.

“Please can I have another kitten?”  Mickey asked.

In a final, fatal lapse in judgment, we brought home another cat. Mickey named her Ketzel – Yiddish for “kitten.” We quarantined her, as the vet suggested,  then slowly introduced her to the rest of our feline family.

Daffy was really not amused.

We found our fluffy towels mysteriously pulled off the bathroom towel bars, with yellow puddles pooling in them. Then puddles appeared everywhere. Mickey’s book shelves. Jonathan’s bed. Marc’s desk. The living room sofa.

“Maybe it’s a kidney problem,” I worried. “Let’s take her to the vet.”

$775 dollar’s worth later, the vet said, “Clean as a whistle.”

“You have to get rid of her,” my mother in law said.

“I can’t. She’s family.”

Instead, I bought a special ultraviolet light like the ones forensic experts use on cop shows to reveal crime stains.  It was worse than we thought. The house was a feline latrine. Daffy had marked nearly every piece of upholstered furniture we owned.

The vet gave her tranquillizers. Then Pet Prozac. No change.  One night Daffy sat in front of the reading lamp, blocking Marc’s light. When he tried gently to move her, she bit him.

“I am so done with this cat,” Marc said.

I called the vet back. “The only thing left I can suggest is a behavioral therapist for pets,” she said.

The irony did not escape us.

I would have done it too. But then my father died suddenly. That meant crowds of  visitors... and Daffy’s wrath.  Desperate, I called Shana.

“Take her,” I begged.

I packed her off with a trousseau. A pricey cat carrier. Buckets of food and litter. Bundles of bedding and toys.  “Daffy’s having a sleep-over with Shana,” I told Mickey.

Shana called that evening. “I put her behaviors on extinction.  She gets Tuna Treats every time she uses the litter box properly. Then I’ll fade the prompts.”

“I’d still put a rubber sheet on your bed.”

“No worries,” she said.

With Daffy’s disappearance, the four other cats reappeared, much like the Munchkins creeping out after Dorothy dropped a house on the Wicked Witch.

“Is it my imagination or do they seem... happier?” I said to Marc.

“I know I am.”

“When do you want me to bring her back?” Shana asked a week later.

“How about never?” we chorused.

It has been nearly three years.  Shana claims Daffy is friendly and well behaved. No sign of Dizzy’s Evil Twin.  She’s pretty pudgy too, from all the treats. Shana admits she’s afraid not to give them. She frets when her fiancé Dave moves in with a Boston terrier named Iggy.

“She swats Iggy if he gets too close, and she eats Iggy’s food right out from under him. Otherwise, she’s an angel. I told Dave all about her but he doesn’t believe me, ” she says, then  describes how Daffy also likes to put her head in the fish bowl. She laps up the fish’s food.  Amazingly, the fish swims up to watch. “I swear, they even kiss!” she says.  She shows me a video on her phone to prove it. One day the fish goes belly up. Daffy misses her pet. She is moping and cranky, so Dave buys her another fish. It lasts six hours.

“I think she scared it to death,” Shana says.

Kind-hearted Dave buys another fish.  Two days later, Shana emails me.

“Last night we walked into a crime scene. The cat and dog looked innocent enough but laying there on the floor was...Daffy’s latest pet. The murderess! I am beside myself.  I don’t know how she did it. We think she picked him up with her mouth and flung him on the floor and then watched him die.”

She adds, “We will make her wait a couple of days before her replacement friend is bought.”

I think Daffy has the upper paw.

“Is Daffy still our cat?” Mickey asks.

“Yes, but she lives with Shana now,” I tell him. “Would you like to visit her?”

“No thank you,” he says.

That says it all.