Lord Voldemort appeared in his lair with an almost inaudible pop. He was emotionally exhausted from his run-in with his former Transfiguration professor, and ashamed at his Death Eaters' performances against a bunch of schoolchildren. To be perfectly honest, he was also a little ashamed of his own failure to kill Dumbledore. All of the participating Death Eaters would be punished for their inadequacy, just as soon as he could think up a good diabolical plan. He would leave them in Azkaban for the time being, since they had proved to be useless anyway.
Perhaps he would call the rest of his Death Eaters to his side, or maybe just Bella and Wormtail. He might have saved Bellatrix from being recaptured and sent back to prison (or given the Dementor's Kiss), but he was still disappointed in her dismal work in the Department of Mysteries, her murder of her idiotic cousin not withstanding. She really should pay for her failure. And Wormtail always deserved a reminder of whom he answered to, of course. Casting the Cruciatus a few times would undoubtedly elevate the Dark Lord's dismal mood.
Voldemort shrugged out of his cloak. He tossed it over his throne-like armchair on his way to the kitchen, to get a nice cold Butterbeer. As it draped over the back of the chair, the cloak made a distinct crinkling noise. As thick black velvet is not usually prone to making crinkling sounds, this peaked the Dark Lord's interest. He turned back from his mission to quench his thirst to investigate. Carefully, with an almost paranoid air, Voldemort slid his hand into the strangely lumpy left pocket of his cloak. Instead of finding a couple of knuts or sickles, as he expected, the Dark Lord's hand encountered something that felt like a bag. A muggle plastic bag, to be exact. Feeling the beginnings of suspicion, Voldemort removed the item from his cloak pocket. It was indeed a muggle plastic bag, sullying the Dark Lord's beautiful cloak with its dirty origins.
It was candy. The red paper label spelled out "Lemon Drops" in yellow lettering, and small misshapen yellow orbs were visible through the transparent lower part of the packaging.
Where on Earth could this bag of muggle sweets have come from? "Dumbledore! He could have slipped them in my cloak pocket while we were dueling!" thought Voldemort.
The Dark Lord immediately dropped the bag. Holding his hand as far from his face as possible, he pointed his wand at it, yelling "Scourgify!" Although not quite satisfied that the muggle diseases that were undoubtedly on the package were counteracted, he decided that the charm would have to do for the moment. He then stepped back from the sinister bag of candy, wand pointed at it unwaveringly. "Lumos!" he commanded, lighting the tip of his wand. Then Lord Voldemort did something very uncharacteristic. He kneeled on the ground. Without touching the offending object, the Dark Lord examined it closely in the wand light. It appeared that the strange shapes were supposed to be reminiscent of lemons. The little sweets sparkled oddly.
Finally satisfied that he could gain no more knowledge from the outward appearance of these "Lemon Drops", the Dark Lord stood up. He backed away from the seemingly innocuous bag of candy, with his wand pointed at it unwaveringly. As soon as he felt that he was at a safe distance, he began casting spells. He searched for enchantments, hexes, curses, and potions. Each time, the result was the same: negative.
"There has to be some kind of jinx on these!" he thought, desperately. "If Dumbledore slipped them to me, he must have had some nefarious purpose!" Still unaware of what that spell could be, Voldemort began casting every countercurse he could recall. Jets of light, and thousands of different colored sparks hit the little plastic bag.
Then, it exploded.
When the Dark Lord recovered his vision, twenty seconds later, all that was left of the bag of sweets was a shriveled, smoking mess. Voldemort waved his wand at the remains, and it disappeared.
"That's that, I guess," he thought. "Now I must go check myself for muggle diseases and such. I did touch that thing, if only for a few seconds." Voldemort turned around, to head to his bathroom. As he did, his eye caught a flash of yellow in the entirely black room.
One Lemon Drop had survived.
Unsure of what to do with the sweet, Lord Voldemort threw away his caution. He bent over, and picked up the sweet. It certainly looked harmless enough. It was even appealing, in a way. The Dark Lord had never really had many sweets before. His childhood in the orphanage had been entirely devoid of good-tasting treats, and later in life he had assumed that one didn't gain status in the world of evil by eating candy. Maybe once, just this once, he should taste something sweet and sugary.
Holding the Lemon Drop in front of him, he cast a quick disinfecting charm. One can never be too careful of those insidious muggle diseases! He then brought the candy toward his lipless mouth, and set it on his tongue.