Felix Blake is an espionage agent working for S.H.I.E.L.D.
Agent Blake, along with Agent Sitwell, was assigned by Nick Fury to retrieve the last of the 47 Chitauri weapons, now in the hands of a down-on-their-luck couple, Benny and Claire, who were using it to rob banks. Blake relayed the orders to Sitwell of intercepting the civilians currently in possession of the "Item 47", collecting the weapon and neutralizing the criminals.
To Blake's astonishment, Sitwell recruited the couple to S.H.I.E.L.D. instead of following the orders. Sitwell also assigned Claire to be Blake's new assistant.