Howard Stark tried to obtain the Ant-Man Suit from Hank Pym for a mission, but after his refusal, and convinced by Peggy Carter, Stark reluctantly sent Pym himself to retrieve HYDRA technology that had fallen into the hands of dangerous radicals.
Pym used the Ant-Man Suit to shrink down and get through the Berlin Wall. At his shrunken size, he encountered a vicious guard dog while attempting to cross the "death strip" of the Berlin Wall, and detonate a "German antipersonnel device" in order to escape. On the other side of the Wall, Pym followed the coordinates that Stark had given him, and he soon came across a wasp, which he used for transportation.
Hank Pym soon located the radicals' base of operation, easily bypassing a pair of guards to enter a room and return to his normal size. He discovered plans for "some of HYDRA's old memory suppression experiments" before hearing screams which he followed to find a room containing a functioning Memory Suppressing Machine with a man loaded inside, screaming in agony. A HYDRA agent ordered the test stopped and asked the subject if he was ready for duty. The man responded that he was, announcing his loyalty to HYDRA. Moments later, the man began to regain his memory and screamed for help, and the HYDRA agent ordered for the man's mind to be wiped again.
Pym shrank again and entered the room, using his tiny size to psychologically torment the HYDRA agent before beginning to destroy the machinery. He then freed the test subject and distracted the HYDRA agents before momentarily returning to normal size and attacking them. He then shrank again and fled on the wasp as additional HYDRA agents arrived.
Back at the S.H.I.E.L.D. Research & Development Laboratory, Hank Pym explained that he destroyed the plans for the Memory Suppressing Machine, and Howard Stark insisted that the Berlin operation was Pym's last field assignment. Pym disagreed, however, insisting that "there's important work to be done in the field that only the Particle can handle," and that "the only way S.H.I.E.L.D. gets the Pym Particle is with a Pym operating it."