i think its 95% a sick tony fic and then hiding it. so that may be a little help, for you awesome dudes out there.
The avengers team (minus tony) + some agents from Shield (hereunder also coulson) goes into save (civilains i think but it might be soemthing else). But inside the building there is a toxic cloud, and the team (minus tony) succumb to it.
Then the next scene i remember is that Tony comes in to save them. But is met with a lot of distaste since he didnt help them from the start.
Please please help me, i have been searching for this fic for so long, and i myself am about to succumb to my own toxic cloud of feels XD