Natasha walked quickly down the deserted back streets, avoiding the few spots of light cast by the occasional working streetlamp, hood pulled up despite the overwhelming heat. Weaving in and out of alleyways and empty streets she kept her head down and moved as quickly as should could, hoping to remain unnoticed.
Glancing around to ensure she wasn't being watch she quickly climbed into an abandoned, run down car she pulled out what most people would assume was an old mp3 player, she plugged it into the radio; switching it on she heard static in the com device and ripped it hastily from her ear. She dug another from her pocket;

"You have less than three minutes until HYDRA are listening again Fury"

"Agent Romanoff we're pulling you off this mission"

"What? Why? It's almost complete. I have most of the intel you asked for, just give me another few days?"

"Romanoff, we have information which suggests you've been made"

"Damn! How?"

"We're not sure yet, we've sent in an evac team; you have one hour to get there"

"Fury, I'm at least an hours drive away, all the intel is back at the hotel..."

"Leave it. Just get out of there"

"That bad huh?"

"It's that bad. One hour Natasha; get there safely"

"Roger that Fury"

Discarding the HYDRA issue com unit and her fake id in the nearest trash can, she began rapidly putting some distance between her and the HYDRA base she'd infiltrated. For five weeks she'd been undercover, steadily rising through the ranks as her linguistic skills far surpassed anyone else's. Her alias was Maggie Jones; a recent graduate of Harvard University ,she was raised across the globe travelling with her parents who were archaeologists, her skills as a translator were desperately needed for several current HYDRA operations and the fact she was fluent in nine languages made her invaluable to them. She was employed to translate documents they'd 'acquired' and therefore gave Natasha a good access to the information HYDRA were spending a lot of time, effort and money obtaining.
When information started coming in about the Avengers, their know allies, their whereabouts, safehouse locations and info on their friends and family Natasha had contacted Fury. He'd advised her to subtly alter the data in the hopes no one would pick up on it. Clint, Steve and Tony had been sent to interfere with the sources of information and try to track and contain the leaks.

Joseph Dunn, agent of SHIELD who was deep undercover within HYDRA was soon in contact with Fury, expressing concerns that Natasha's cover wasn't all as concrete as they'd hoped. He advised Fury to withdraw his asset before it was too late. Two days later Dunn was found dead; apparent suicide. That was when Fury contacted Natasha and arranged her removal.

Three blocks from where she'd ditched her fake id and anything tying her to the hydra operation, Natasha found an inconspicuous car which was easy enough to steal; hot wiring it, she took off for the evac point. She knew her situation was dire based on the brief conversation with her boss. He'd never once pulled her off a mission and asked her leave intel behind; she'd been reprimanded on several occasions, and almost fired once for leaving intel behind (even if those decisions had saved more than one life in the past, including her own).
The council had never been her biggest fan and were just looking for an excuse to dispose of her.

Several hours later and Fury was going out of his mind.
Clint, Tony and Steve hadn't made contact when they'd been scheduled to, and Coulson's attempts at contacting them had all failed.
The team that'd gone to get Natasha had reported a problem before going radio silent.

"Director Fury, these are the images from Mexico"

Hill passed a file of images to Fury over the desk. They showed dead bodies, a SHIELD issue quinjet in flames, explosions and gunfire; an ambush. That was the team
sent in after Natasha.

"How many dead?"

"All of them sir"

"And Romanoff?"

"No sign of her sir"

"Coulson heard from his team yet?"

"Nothing yet, JARVIS is offline, coms are dead, their last know location was a bust..."

An email flashed up on Fury's computer, it was marked as urgent and came from an unknown source. He moved to open it with Hill peering on;

Two simple words appeared on screen before the email wiped itself without a trace;

'FOUR DOWN...'