The film takes place during World War II, where Steve Rogers (Chris Evans) tries to enlist in the United States Army, but is rejected due to his physical limitations. However, he is approached by Dr. Abraham Erskine (Stanley Tucci), a German defector who works for the United States government. Erskine recruits Rogers for a top-secret government program that aims to create a super-soldier.
The CAP-Download protocol was an emergency plan created by Dr. Erskine to ensure that the serum's formula and Steve Rogers' enhanced abilities would not be lost in the event of his death. The protocol would allow S.H.I.E.L.D. to recreate the serum and reactivate Captain America's enhanced physiology, should the need arise.