"Christopher Murphy and Hans Thompson." Natasha said. "I'm not completely sure Hans Thompson isn't an alias, but it's the best I can do right now." She and Clint were standing in one of Stark's labs, with most of the Avengers. Banner was AWOL. Not that unusual.

"How did you even get that much?" Rhodes asked.

Clint shrugged. "There's an NYPD chief who I was sent to attempt to seduce a while back. Didn't go so well, he's a faithful husband, but he thought I was sweet, he knows – well, thinks - I'm a federal agent. I can get small favours from him once in a while."

"Small favours?"

"Like running a licence plate, seeing the licence of the last person to get pulled over for speeding in that car. What do you know? It's Murphy."

"What to the code words they're using mean?" Rogers asked

Nat dropped her list of code words on to the table.

"Ithun's a nettle agent gas." Barnes said, without looking at the list.

"Phosgene." Nat specified.

"That's old." Rogers said. "Heavier than air, colourless, smells like musty hay, can kill you later even if you only get a bit of it." Wilson looked questioningly at Rogers. "Everyone expected the Nazis to use it, like in the Great War. Don't think we ever actually ran in to it."

"But that's not the one we're dealing with." Clint said. "Sandrauriga is Tabun."

"Jarvis, pull up a schematic of the synthesis process for Tabun."

"First generation nerve agent, Sir." Jarvis said. "Might I speculate that 'Valkyrie' is code for a cyanide salt of some sort?"

"It is." Romanoff said. "It's what they have in the false teeth."

"In that case, Sir, we might reasonably assume they'll have at least some Tabun prepared days after they receive the shipment of dimethylamidophosphoric dichloride."

"And we don't know where the lab is." Rogers said.

"I don't think the lab exists yet. There's just an unnamed chemist who can handle the processing." Clint said.

"We need to make sure the shipment never happens." Nat said. "Cut off at source. We think Murphy's making the payments as well as calling the shots. If he dies…"

"Are you suggesting we assassinate?" Rogers asked.

"It's the safest way to remove the threat." Nat replied.

"That makes us Judge, Jury, and Executioner."

"Steve, he's using HYDRA buzz words and code words to discuss acquiring chemical weapons." Barnes said flatly. "Is this really going to cost you any sleep?"

"Pre-emptive strike." Tony said, eyes still fixed on Jarvis's chemistry schematics. "This stuff is lethal by inhalation or skin contact, even in tiny doses. You drop even that much of it on to a subway train in rush hour… It's not even just the people there. It's the EMTs and cops who start pulling the bodies out. They die too."

"Do we know for sure that killing Murphy stops this?"

"At bare minimum, it slows it down."

Steve sighed heavily. "Do you have a plan?"

Nat drew a breath. "Sort of. The real problem is that nobody can know it was us."

"So using any Stark Tech is out of the question." Stark said.

"Car accident?" Barnes suggested. "You just need an isolated stretch of road." Stark went suddenly very still. Barnes didn't seem to notice. "Shoot a tyre out, run up and clean up what's left. No bullets, just blunt trauma."

"He lives in New Hampshire Estates. There are no isolated roads he travels routinely." Nat said flatly.

"How much do you know about where he's going to be?" Barnes asked.

"We have one appointment." Nat said. "He said in another conversation earlier today that he's going to be at a birthday party for another senator at The Washington Wharf hotel on Friday night."

"Then I," Clint said, "being a small-time kitchen hand called Carl Brunswick, got another small-time kitchen hand called Dorran to tell me about this fancy job he's been hired to. A hundred invites, each with a plus one."

"That's a lot of witnesses." Barnes said.

"And a lot of cover." Nat said.

"And a lot of potential collateral damage." Rogers said.

"You gonna put something in his drink?" Barnes asked.

"It's an option." Nat said. "We'd need to get hold of a suitable poison; rapidly water soluble, common enough that it would be hard to trace back to us, rapidly acting enough that he couldn't get to the urgent care centre five minutes away by car in time."

A beat. "Okay, yeah, problem." Barnes said.

"Cyanide ticks most of the boxes, but that's potentially tricky to get hold of."

"You didn't say you were worried about getting in there." Rogers said.

Nat shook her head. "Getting in the door isn't a problem. Getting his attention isn't a problem. The challenge is killing him and getting away clear."

"Do you have to be the one who does it?" Stark asked. "What if you lure him out to the street and some 'masked thug' mugs him and goes too far? Like Batman's parents. J, pull a map of the surround up, in 3D."

They looked. "Not a great place for muggings." Nat said, looking at the wide streets, lined with street lamps."

"Or in to the path of a sniper." Rogers said.

"So let's think about nests." Clint said.

"That balcony there, on the second floor." Nat said. "By night, with lights on inside, you won't see anything through them, even if the blinds aren't drawn."

"So we shoot at that." Clint said. "Hey, Jarvis, what's this building?" Barton waved at the facing towerblock.

"Apartment block, sir."

"Any vacant ones?"

"Yes, sir. Second floor, East facing, and eighth floor, east facing."

"Damn." Barton said. "Common areas?"

"First floor."

"So that would be…" Clint traced the shot with his hand. "Up and over… are those solid railings?"

"Glass, sir."

"Damn." Clint said. "What else have we got? The parkland over here's no good."

"The balconies are staggered." Barnes said. "Straight down from the top of the roof."

"With Nat standing right next to him." Clint ran a hand through his hair. "Straight down is hard. Is there no other way?"

"That side's the Potomac River." Stark said.

"I can do it." Barnes said.

Everyone stared at him.

"That's… what? A hundred feet? Hundred and twenty? That's nothing."

"Dangling the gun off the edge of a roof?" Barton asked.

Barnes lifted his metal arm. "This was made for sniping. It locks. Forms its own tripod. I'm assuming I'm using unmarked slugs?"

"Probably best." Romanoff said.

Stark bit his lip. "Might be able to do you one better.

"Just give me twenty minutes with the gun you want me to use before you send me out." Barnes said.

"Buck-" Rogers started.

Barnes looked at him. "I can do this, Steve. I was made to do this."

"You weren't made to." Rogers said. "You were trained to."

"I know I'm supposed to keep low, but let me at least kill one of them. Just one."

Nat looked at Barnes for a long moment. Something there echoed in her. He had red in his ledger.

"How are you going to get up there?" Barton asked.

"See the fire escape stairs on this corner?" Barnes asked. "I was going to climb the stairs to the top fire escape here and climb the rest of the way."

"You'll be really visible there." Rogers said.

"High-vis jacket, hard hat, and a clipboard." Nat said. "You can walk in to almost any public building."

"With a huge gun?" Stark asked.

Barnes thought for a moment. "We said no Stark Tech anywhere near this, right?"

"Right."

"Are Sam Wilson's wings Stark Tech?"

"No." Stark said. "But they're also kind of unique."

"And emit less noise and light." Nat said. "By night, he'd be very hard to spot."

.

About an hour before sundown on Friday night, a white man with short brown hair, wearing high-vis vest, a black musto jacket, a white shirt with a red tie, a white hard hat, and carrying a clipboard, started up the fire escape stairs of the Washington Wharf hotel. He went slowly, methodically checking bolts and door fixings as he went. By the time he was half-way up, nobody was paying him any attention. When he got to the top floor, the man tucked his clipboard inside his coat, and jumped both feet up on to the railings. Fourteen floors from the ground. Then he bounced up, catching the edge of the roof with one hand, and pulling his whole weight up, left-handed.

The roof was deserted. Bucky Barnes slid himself between the two huge water tanks and took off his high-vis and coat, then put them back on in reverse order. From inside the hard hat, he took a black face covering. He put it on and put up the hood, then James Buchanan Barnes lay down in the gap, almost invisible in the late afternoon shadows, and curled up, waiting for dark.

When the darkness had fully settled, Bucky Barnes heard a whoosh of wind, then a soft thud, before he'd even stood up fully. When he emerged from between the tanks, his hard hat was gone and a black holdall lay where it had been. Serum-enhanced eyes showed him the glint of metal disappearing in the wind. He opened the bag and started putting its contents together.


Yes, I researched the synthesis process for an assortment of chemical weapons before I wrote this.
Yes, I did wonder why I decide I have to go there.