The TARDIS caromed across the eleventh dimension, threading its way through the ether towards its destination. Inside its cavernous control room, Martha Jones looked at the view screen as it came to life. "Is that where we're headed? Earth?"

The Doctor seemed lost in thought. Martha jabbed him in the shoulder. "Sorry. I was trying to remember when I was last here. It was around this time. I don't want to run into myself again. Last time it was a bit of argy-bargy. You might not believe it, but I used to have a problem getting on with others-Well, others of me, other I? -previous me, my selves. Don't know about future me, haven't met him yet. Still…"

Martha cut in. "You said we were here for a reason?"

"Most points in time are in flux-" the Doctor said while wrestling with the TARDIS controls as chimes sounded. "-but some points are fixed. They cannot be changed no matter how much you try to interfere. Most of these are big events, turning points in history. But some are small, seemingly insignificant moments which form the nexus of a crisis, the origin of storms. We're here." The wheezing sound of materialization faded and the TARDIS seemed to groan. "One of these fixed points right here-today-in this supermarket in Cincinnati, Ohio, United States, Earth, April 11, 2012 A.D."

"Are we just here to observe, then?" Martha asked.

"We're not here just to observe."

"But if this one of those that absolutely can't be changed…"

"It is, and we're here because someone has changed it." The Doctor ran to the door and opened it. An almost blinding fluorescent light assailed them. The Doctor stepped through swiftly, Martha following close behind. A noisy procession of shopping carts sped by.

"Move, you moron!" said a woman angrily. "Billy, keep up!"

Martha looked around, puzzled. "So, what's so important about a supermarket?"

The Doctor stared ahead, seemingly at nothing in particular. "This is the first in an inexorable chain of events which leads to the Coupon Singularity of 2015. One shopper is at the center of it."

"Where's my envelope?" Angry woman again. "Hey, moron! Wake up."

"Is that her?" asked Martha.

The Doctor nodded. "Today's the day she breaks the bank of the Coupon Hegemony."

"Is that what's supposed to happen?"

"Yes-and no. Something's not right. Can you feel it? There's a chill in the air." The Doctor produced his all-purpose tool, the sonic screwdriver, and began scanning. "Why is it so cold?"

"We're in the frozen food section." Martha opened a glass door and a rush of cold air hit them.

The Doctor turned his head. "No time for shopping, Martha. We've got work to do. Follow that cart!" He stepped off along the route taken by Angry Woman. "Her name's Amanda," he whispered to Martha, sotto voce. "Coupon Queen of Ohio. We just need to bide our time until she checks out." As they turned the corner at the end of the aisle, they nearly ran into Amanda's caravan.

"Are you following me?" Amanda growled. Her beady eyes glared at them.

The Doctor froze, his eyes widened with surprise. "No," he managed. "No, definitely not, not following you… at all. Sorry," He deliberately pivoted on his left heel, spinning around toward Martha who was hiding behind him and gently nudged her away. "Hang back a bit." He randomly pulled a bag off a shelf and began to walk in the other direction. "Craisins? Cranberry and raisins. Brilliant! Martha, look at this."

"So how did you know someone is trying to change this point in time anyway?" Martha asked.

"Well, the TARDIS told me. When critical points are altered, disturbances are created which reverberate through the time stream. If you are attuned, you can perceive the alterations. I used the TARDIS' circuits to look for anomalies. I could train you to see it, too."

Martha laughed.

"You see," the Doctor continued, "your proto-response conditions your total response towards which your fully equilibrized organs of apperception subconsciously tend."

"Oh when you put it like that!" Martha said. "Doctor, look."

A crowd was forming at the checkout line ahead.

"She's checking out. Allons-y!"

As they approached the edge of the crowd, the scanners beeping seemed to grow louder. The Doctor grinned. They watched as Amanda and her husband, Billy, began to unload the contents of their 5 carts. "Exciting, isn't it?" he whispered.

.._BEEP BEEP BEEP.-_.

Nearly an hour later, the crowd had dwindled and Martha yawned. "I don't know how much longer I can stand here. I'm bored out of my mind."

"Shh! There starting to scan the coupons now!" the Doctor whispered.

.._BEEP BEEP BEEP.-_.

"Here comes the magic," said Amanda. "Billy, where the Hell are my coupons?" I need the other envelope now!"

"I feel like I'm at the Olympics."

"_-_INVALID COUPON-.-.." said a mechanical voice.

"What?" Amanda growled.

The cashier gestured to the store manager who was watching nearby. The manager stepped to the register. "I can do an override." He tapped at the keys.

".- _-. AUTHORIZATION DENIED-.. INVALID.-._-TRANSACTION TERMINATED-..-.-"

Martha tugged at the Doctor's sleeve. "Doctor, that voice. "

Amanda was screaming. "No! This can't be happening!"

The register seemed to vibrate. "-. _ -._ -COUPON NOT RECOGNIZED.._-_ WILL BE EXTERMINATED. _-._-"

The register began to move. With a metallic ringing, it separated from the surrounding enclosure and began to risk out of the floor. A single glowing eye manifested itself out of a tangle of machinery. Sparks flew as a machine tore itself away from network cables and plastic barriers.

"Daleks!" the Doctor hissed, and his mouth remained open in a rictus of alarm.

"_-_. _-TRANSACTION CANCELLED. -_-EXTERMINATE!"

Amanda snarled. "What are you?"

"-I AM, DALEK SKU.-..,_-"

"I don't care who you are. Nobody messes with my coupons." Amanda grabbed a canned ham and hurled it. It bounced off with a clang spinning the Dalek eyestalk around. Amanda followed with a shower of Mountain Dew expelled forcefully from a shaken bottle.

The Doctor turned to Martha. "She's got the right idea. Quick, while it's still changing. We have to confuse its senses. Yogurt, popcorn, whipped cream, everyone! If you value your lives, do not run! Hit it with everything you've got."

Several members of the crowd converged on carts and shelves and began to pelt the Dalek with whatever was within reach. They threw canned peas, cauliflower, pork tenderloin, and Pop-tarts. They launched frozen waffles, asparagus spears, chunky salsa, tartar sauce, Boston baked beans, and mozzarella. They let loose a barrage of Little Debbie Oatmeal Creme Pies, a cannonade of Hamburger Helper, a salvo of mixed nuts, a broadside of mango chutney, a volley of organic granola, and a fusillade of she-crab soup.

"_-_-. YOU WILL DESIST. RESISTANCE IS FUTILE. CARBONATED BEVERAGES ARE NOT COMPATIBLE WITH OPTIMUM EFFICIENCY. CEASE THE BOMBARDMENT-OR YOU WILL BE EXTERMINATED-_-.;"

A deluge of Purina Ferret Chow, 9 volt batteries, and port wine cheese logs rained down on Dalek Sku. He was bombarded by baguettes, Fruit Loops, and Mike's Hard Lemonade. His electronic eye was obscured by a torrent of hummus, Cool Ranch Doritos, walnut chicken salad, and Texas toast.

"-..-PROCESSED MEAT AND CHEESE CANNOT DAMAGE THIS UNIT-DAMAGE THIS UNIT_-..-..THIS UNIT. "

A pineapple grenade slammed into its dome.

"His defensive screens are down!" said the Doctor pulling out his sonic screwdriver and activating it in one fluid motion. The Dalek exploded in a cascade of sparks. "Something must have contained erythorbic acid. Very toxic to the Dalek physiology-if you can get it through that thick shell. Deadly to Daleks, a harmless preservative to humans. Well, mostly harmless."

The manager stepped forward. "Okay, everyone. The danger's over. I'm going to ask you to please walk to the exit…"

"No," said Amanda. "I am not leaving until I get my extreme transaction done."

The Doctor stepped forward. "That's right, Amanda. You're not going anywhere. Not just yet. You not from around here, are you?"

Amanda said nothing but stared at the Doctor intensely.

"What's happening?" said the manager.

"This woman is a monster," said the Doctor.

"We all knew that," said Billy.

"She's not a local monster. She's not even from this galaxy. Oh, you've come a long way, you have! But why? Why here, why now?"

"Because," Amanda snarled, "This is where the coupons are." At that moment, she seemed to turn inside out and a mass of translucent tentacles erupted out of her.

"Eww," said Martha.

Billy screamed as a barbed tentacle encircled him and expelled acid. With a crackling sound and a sickening smell, Billy began to melt.

"Ewwwww," said nearly everyone.

"Arrgggh," said Billy.

Back in the TARDIS, Martha asked "So is that it, then? Has the timeline been sorted?"

The Doctor sighed pensively. "Well, yeah, close enough. Main thing is we've prevented total retail disaster. Oh, there's still a storm coming but nothing that isn't inevitable, necessary even. Throughout the galaxy worlds go through parallel development." He flipped a switch. "The same pattern repeats itself again and again: the invention of the wheel, the steam engine, nuclear power, extreme couponing…" The Doctor pulled his hands away from the console. "Where to now? Your choice. Shall we see the Face Dancers of Bene Tleilax? Or how about Mallworld?"

"Any place but Mallworld. I have had my fill of shopping."

"Right. Las Vegas it is."

NEXT WEEK:

LAS VEGAS, NEVADA - Gold and Silver Pawn Shop

RICK: How did you get that blue box in here? Do you want to sell it or pawn it?

DOCTOR: Oh, it's not for sale.

RICK: I'll give you $100 for it.

DOCTOR: $100?

RICK: Actually it's too big. I don't know where I can put it.

MARTHA: Doctor, it's a monster!

RICK: No, that's just Chumlee.