(Author notes updated, 18th October, 2012, regarding capitalisation)
Disclaimer: I am not J K Rowling. I do not own Harry Potter. I am not Leslie Charteris. I do not own The Saint.
Note: Alternate universe crossover warning! This assumes a Harry Potter universe in which The Saint (approximately as depicted in the original Charteris books) existed. I have taken the liberty of imagining The Saint had a couple of sons, one of whom had a daughter who married James Potter (in place of Lily Evans) for the purposes of dragging him into this.
In which witty badinage and more lethal things are exchanged, and Miss. Sophie Theresa Potter is technically the last one standing
"So, it's just you and me now, Voldy, and my great-granddaughter. And any reinforcements that either of us have on the way. We did get a telephone call out before you so rudely interrupted us."
The Dark Lord eyed his nemesis warily. The one adult wizard in the house had provided minimal resistance. The muggles had proven rather more… problematic… and seven of the Dark Lord's most loyal followers were either dead or incapacitated. Had the Dark Lord attempted this on his own, it would have turned out to be a suicide mission.
The man the Dark Lord now faced must be close to eighty, but was horribly spry and dangerous for all of that. In the Dark Lord's own youth, before Albus Dumbledore had stolen Tom Riddle away to Hogwarts, this man had been a legend across half of Europe. The icy blue eyes were unflinching in the face of the Dark Lord's stare, and there was nothing but cool resolve and defiance for the Dark Lord's legilimency to find. For a muggle, the man had a remarkably closed mind, and the Dark Lord dared not make the effort to probe deeper and risk missing something the man was physically doing.
"Templar." the Dark Lord acknowledged. He was starting to regret now going after the Potters. But a member of an ancient and noble pure-blood family marrying a muggle was too big a slap in the face for his cause to overlook for long. Unfortunately, the muggle James Potter had married had turned out to be Simon Templar's granddaughter, and these muggles could fight.
The Dark Lord had a wand pointing at Templar. It was the wand of one of the Lestranges, as he dared not risk his own wand in this dirty fighting. The first Death Eater through the front door had been smashed over the head with a frying pan and his wand bodily grabbed and snapped. The next had had a bullet put in his head. After that the Death Eaters and the Dark Lord had had to become a little more… circumspect… and creative in their approach to this particular house in Godric's Hollow.
A raid by a gang of Death Eaters led by the Dark Lord on a house full of muggles should have been a piece of cake. It had turned into a massacre – for both sides.
"Since you appear to be amenable to witty banter, please convey my regards to the treacherous secret keeper, should you meet with him again." Simon Templar continued. "James, poor bloke, was of course absolutely convinced he could trust the man. Alas, the only good judgement James has apparently ever shown in his life with a big decision was in marrying my granddaughter. Fortunately, on my own side of the family we were inclined to be considerably less trusting, and insisted on additional family support. I'm pleased we were able to present you with a challenge. You know you really should have brought more minions, Voldy, if you didn't want a fair fight."
"My agent in James' camp was under-informed of just who Mrs. Potter's relatives were. We would have razed the house from a safe distance or come with a job offer had we been better informed." the Dark Lord replied.
Templar had a throwing knife in one hand, and some sort of muggle device with a number of buttons on it in the other. Templar clearly had some sort of plan. Whether or not that plan extended beyond mere bluff, the Dark Lord had yet to determine. And it was intriguing, to be conversing with an enemy for once, rather than just avada kedavra, dark mark, and move on.
"Ah well. Given neither of my sons carries the glorious name of Templar, perhaps that can be excused." Simon Templar said. "That was their decision so that official busybodies should not busybody them quite so much. And desire to make names for themselves, of course. A job offer might have amused us, but whilst corrupt officials and criminals are fair game, targeting innocents puts you well and truly on the side of the ungodly. Had you confined yourself to more specific targets, we might have applauded…" He shrugged.
The man's composure was unbelievable. He stood here, looking death practically in the face, and was all but laughing at it. A mere muggle, with no horcruxes or get-out-of-death-free cards to play.
The sound of crying from an adjacent room cut through the air.
"Excuse me please." Templar said. "She's asking for attention – my attention, as you and your followers appear to have killed her parents and her great-uncle. Would you mind either buzzing off to find someone else to bother, or getting it over with and attempting to do whatever it is you intend to do?"
The Dark Lord raised his wand, as a knife flashed through the air, and a thumb came firmly down on a button. An explosion rocked the house, and then all that there was to be heard was the sound of an infant crying and the wail of approaching sirens…
Because an alternate universe with a confrontation between Lord Voldemort and (even an elderly) Simon Templar was interesting to write... And it looks like it's turning into something longer.
Update (18th October, 2012): Canon capitalises some words (such as 'Devil's Snare' and 'Bludger') but not others (such as 'mandrake' and 'broom'). I'm unclear as to what rules govern this in canon in most circumstances, and unless such words seem to me to be proper nouns, pseudonyms, or to otherwise merit particular emphasis (as with 'Unforegiveable Curses' in the latter case) I will be foregoing such capitalisation.