Somebody's got it in for Sarah Jane this time...

The only markings on the package were the words '13 Bannerman Road' written in red ink. Sarah Jane noted that in the addition to the lack of a return address and the fact that it had been delivered on a Sunday, it felt oddly light. Curiously, she opened it up to find another box inside. And another inside that one.

"If this is some sort of joke..." she said to herself as she went through two more boxes. The third box contained two boxes- one about the size of a ring box, the other larger. She opened the smallest one first.

Inside was a tiny electronic device no bigger than a pea that vaguely resembled an insect. After a cautious examination, she set it aside and opened the other box. This one contained a sleek x-shaped device with a few buttons on it. She set both devices down on the kitchen table and considered them for a moment.

"K9?," she called, "I need you to run a scan on something."

"Coming, Mistress." From the next room, she heard him whirring as he made his way over.

Suddenly, the pea-sized bug device switched on with a sharp beep. Too fast for Sarah Jane to catch, its wings activated and it flew out of the room. She heard an electronic screech and-

"Mistress! Harmful frequency detected! Primary functions have been disrup-disrup-disrup-"

"K9!" She ran from the kitchen to see him spinning in place haphazardly. Behind her, the other device glowed brightly and shot a ray of energy that hit her squarely in the back. Sarah Jane was aware of a brief tingling sensation before she hit the floor. Scrambling to her feet, she realised she was now surrounded by fabric. She pushed it aside awkwardly, her limbs not responding properly.

Wait a moment...these were her own clothes! And were those...paws? Her paws? She looked behind her to see a tail. A cat? she thought, I'm a-

"Intruder detected," came a crisp electronic voice. She turned around, now looking up at K9, to see he had regained control of his motor functions and was facing her.

"K9?" Okay, so she was a cat that could talk.

"Intruder detected," he said again.

"K9, it's me." The laser gun extended from his snout and she backed up a few paces. "NO, K9! It's me, it's Sarah-"

PEW!

A scorch mark appeared where she had been standing. She took off running on her new legs, claws slipping on the tile kitchen floor. "Initiating chase mode," said K9 as he trundled after her. Sarah Jane did a lap around the table, dodging lasers, then made a break for the living room where she hid behind the TV. She held her breath as she heard K9 whirring along. Why hadn't he recognised her? Even if he couldn't, he never reacted this way to cats. Something was seriously wrong.

Everything was silent for a few seconds. Then...

"Mistress?"

She hesitated, then replied, "Yes, K9?"

"Harmful frequency detected in this room. My higher functions have been affected."

"Can you find the source?"

"Negative. Scanner is impaired. Recommended action- locate and disable source of frequency."

She had a sneaking suspicion it was one of those two weird devices from the box causing this. "All right." She emerged from her hiding spot. "Just don't-"

PEW!

At least whatever was interfering with the tin dog was throwing off his aim. She jumped back just in time, fur standing on end. "Down, K9. Do not fire."

"Yes, Mistress."

Once more, she stepped out from behind the television only to be shot at. "K9!"

"Mistress?"

She sighed. This was going to be tricky. "Do not fire at the cat." When she heard his affirmative, she tried to come out again but he still shot at her. This time, she ran behind an armchair. "Stop!" she cried. K9 paused halfway to her new refuge.

His ears swivelled. Between the television and the chair there were now a series of scorch marks on the wall.

"K9 can you hear me?"

"Affirmative."

"Who am I?"

"Vocal patterns identified as Mistress Sarah Jane Smith."

Good, he still knew who she was. "Now listen, K9- you know it's me. You can hear it's me. But I don't look like myself right now, do you understand?"

"Affirmative, Mistress."

"In fact, I look a lot like a cat at the moment, understand?"

"Understood."

"You are about to see a cat that sounds like me. Do not shoot the cat that sounds like me. Do you understand?"

"I understand perfectly, Mistress."

Sarah Jane relaxed. "Good," she said as she emerged from behind the chair. "Now, I think I know what's causing-"

PEW PEW PEW PEW!

Well, she was definitely going to need new curtains after climbing up them. And she'd have to replace all the broken picture frames on the mantle, and then do something about all the burn marks. But for the moment, she was focused on staying hidden under a throw pillow and blending in with the sofa. Thankfully, K9's scanner was still offline, so he didn't notice her as he trundled about the room.

"Oh, K9..."

"Yes, Mistress?" he asked, antennae ears swivelling towards the sound.

"Let's try this one more time. Who am I?"

"You are Mistress Sarah Jane Smith."

"All right. Now, suppose for a moment that I've been turned into a cat. Am I still Sarah Jane?"

"Yes, Mistress."

"And just because I am the same person in a different form, that does not make me an intruder. Right, K9?"

"Conclusion is logical."

"So you won't shoot cat-me."

"I will not shoot the Feline-Mistress."

"What was that again?"

"I will not shoot the Feline-Mistress."

"...put away your laser, K9."

He obliged. She slowly pushed the throw pillow away...

...and scurried under the sofa as bits of bunt stuffing rained down behind her. She really ought to have made a break for the stairs, but at least he couldn't get low enough to get a clear shot at her down here. As he paced along the perimeter of the sofa, she peeked out and saw the metal bug clamped on the underside of his neck. If she could just get close enough!

"K9, I've found the source of the frequency. It's stuck to you."

"Sensory error: I cannot detect source. Assistance required to remove."

"I'll remove it, I just need you to shut down first."

"Yes, Mistress. Initiating shut down sequence..."

With a low whine, his head and tail drooped down and the light in his eyes switched off. After a few seconds, Sarah Jane crept out from under the sofa and tapped his metal casing with a paw. When he didn't move, she did it twice more. Cautiously, she moved to his neck and scratched at the bug with her claws. It barely wiggled; she'd need to get at it from a different angle. Checking to see that he was still unresponsive, she hopped onto his back and reached around.

"Intruder detected! Intruder detected!"

"K9, no!"

Quickly, he rolled back and forth to try and knock her off, but she clung tightly, not about to give up. She scratched again at the bug, loosening it further, and he rotated his head around.

PEW PEW PEW!

She leapt off, spun around, lunged at his neck, and bit off the bug. At the same time, he jerked forward and knocked her back. She hit the floor hard and had a coughing fit, realising she'd just swallowed the device. While she lay gasping, K9 turned his head around the right way and approached her.

Before she could run, he extended his scanner at her and beeped. "Identity confirmed- greetings, Mistress." He wagged his antennae tail.

"Oh, K9," she said, the relief evident in her voice. "You're back to normal."

"Affirmative." For a moment, he beeped and whirred again. "Mistress, I detect recent use of a type-65 molecular transmogrification device. You are currently in feline form."

"You don't say..." she said, getting to her feet. "Is there any way to reverse the change?"

"Affirmative. Transformation is temporary, and reversals typically occur within ten to twelve hours."

"Surely we can do it faster?"

"Certainly. The process is simple..." K9 trundled along into the kitchen to examine the device.

Finally, thought Sarah Jane, I've had enough of this nonsense for one day.