Jasper Sitwell became a S.H.I.E.L.D. Agent after having been the top student of his class at the S.H.I.E.L.D. Academy. He became Nick Fury's assistant, at one point even filling in for him as temporary Director of S.H.I.E.L.D.. Later, he acted as S.H.I.E.L.D. liaison to Stark Industries.
At one point, he fell in love with Whitney Frost who turned out to be the leader of the Maggia.