The Agent Arrives in Time
The Agent moved silently enough that even a werewolf would have had difficulty hearing him. It might have been from silencing charms on his feet.
Anyone observing him would have noted bits of bright blond hair peeking out from under a navy blue watchcap, and he was wearing a black turtleneck over similar black pants. Of course, being disillusioned, nobody was observing him.
The muffled "pop" of his handgun was inaudible over the sounds of fighting going on inside the house, and the 'Wizard Special' round passed cleanly through Peter Pettigrew's neck, severing his spine just below the skull. The price of failure to practice "Constant Vigilance".
The Agent came around the wall and into the open doorway fully ready to shoot again. Three quick "pop" puffs followed and Voldemort's spine was shattered in three places between his mid-back and his pelvis. The Agent had not won the Gold Medal in International Free Pistol seven times (under various names) because of his good looks.
Two more "pop" sounds in the sudden quiet and both of Voldemort's shoulders no longer had working joints, and his arms were useless for wand or wandless work. The Agent dropped his disillusion charm.
The Agent moved forward silently, noting James Potter was still breathing, a good thing, and with the toe of his boot he flipped Voldemort over onto his perforated back.
A scalpel sharp combat knife carefully nicked the subclavian artery, speeding the bleeding out from the bullet wounds. This was deliberate, as the operation called for a relatively slow death for Voldemort, so the secondary goal of the mission could be accomplished.
Voldemort's red eyes could not settle on rage or fear as he felt life slipping away while his magic was stripping his marked followers of their magic, and then their life force, in a desperate effort to keep him alive.
Here and there, about the UK's hidden magical enclaves, various 'solid upstanding citizens', as well as characters of lesser repute, collapsed in agony, grasping their left forearms. Hogwart's newly hired Potions Professor was not exempt. Fortunately he was not in a class at the moment.
Various magical artifacts which had been defiled and hidden were stripped of their contents as the flow of magic coming from the various Dark Marks slowed to a trickle.
A crystal pyramid was placed on the dying Dark Lords forehead, as the Agent spoke.
"No wraith for YOU, Riddle."
As the light slowly faded in the red eyes, the black mist that attempted to escape was sucked into the crystal, changing its light yellow color to obsidian black.
At just that moment Sirius Black arrived with his wand drawn, and with battlefield honed quickness, took in the scene.
Staring at the muggle dressed Agent, he sputtered "Who the Hell are YOU?"
"Put down that stick before you make me hurt you" was not the answer he expected, and the rock steady barrel of the pistol, zeroed in on his navel, promised pain and/or death before he could get off a spell.
Not wanting to join the unmistakable corpses of Peter and Voldy, Black made no move to try to cast, but neither did he lower his wand, having no idea what was going on.
Before much else could happen the belated apparition noises of various Aurors broke the silence, perennially late to the scene, yet again.
The Agent repeated his demand that they lower their sticks with the promise that if they did not comply, more than one family would be receiving a black notice from Gringotts tonight. The Mexican standoff dragged on for seconds that seemed like hours, until the Agent reminded them that they needed their Healer to attend Mr. Potter's injuries.
As the Healer ran forward, the Agent permitted him to pass, and called the senior Auror present to come forward, as he fished a leather wallet out of his pants pocket. The pistol never wavered.
Handing the wallet to the Auror, he kept his eyes trained on Black and the rest of the late-comers, watching for any 'tell' of treachery.
The Auror flipped the case open to a badge and ID Card.
"Oh Bloody Hell!" was his first response and "Stand down!" followed at once.
"Yes, you will find I am authorized to operate in your so-called 'Wizarding World' from the very highest levels; from the ICW, the United Nations, NATO, MI-5, and, oh yes, Her Majesty the Queen, and her Royal Wizard."
At that point he put the pistol away and it disappeared from sight, totally. Black surmised the holster was under its own combat charms, just like his wand holster was.
Behind him the Agent heard footsteps of Lily Potter coming down the stairs and the half muffled cries of the baby she was carrying one-handed, on her shoulder, with her wand in the other hand. Taking in the scene before her she waited until the lead Auror moved to her side and displayed the wallet and its contents.
Looking closely at the Agent in front of her she gasped. "I've seen pictures of you from the 1930s and 40s, Simon Templar."
"Well, I've not been "saintly" for many years. Keeping one identity, as the non-magicals age around you, is difficult at best. These days, I am working for the same agency I was with in the 1960's and 70s, but my IDs all read "junior" today, so I suppose I am my own son, now. Since my last partner retired, due to age, as well as accumulated damage, I am operating … solo these days." An ironic grin flashed briefly across the handsome face.
"Yes, Her Majesty's government requested magical help, and I was currently available. After all, I've been needed to investigate vampire cases in Romania, not to mention werewolves or the the occasional demon some magical in THRUSH decided to call up and unleash. If anyone cares, I am temporarily down on the books, here in the UK, as 'double O nine and 3/4'. All for 'the greater good' you understand."
"Illya Kuryakin, 'Junior', at your service."