Nick Fury, Maria Hill and Phil Coulson

You're a pretty gifted person. Both in intelligence and in your combat skills, you have done too much work for your own benefit since you work alone. And that's why you're considered dangerous if you're on the wrong side. So, SHIELD has been watching you for quite some time... Almost five years... Nick Fury discovered you through somewhat curious sources of information, from criminal gangs to potential coworkers who know your modus operandi. From there, SHIELD has shown interest in your work and that you can be of great help and convenience to them.That's why... Nick Fury, Phil Coulson and Maria Hill have made a plan to try to convince you to join them, they have no doubt that it will be a big task, but they have to convince you. Today was just an ordinary day for you. You went to buy something for breakfast, and when you got home... They were sitting in the living room

— We're from SHIELD, don't force us to call for reinforcements. said Fury in a stern tone