On a cruise that started in mid 1942, and having already sunk three ships, on 27 September Stier encountered the Liberty ship SS Stephen Hopkins en route from Cape Town to Paramaribo.
Closing in foggy conditions the 2 ships sighted each other around 0852 at a distance of 4,000 yards. Gerlach sent his men to action stations; the master of the Stephen Hopkins was suspicious of the unidentified vessel and did the same. The Stephen Hopkins had only a small defensive armament, 1 - 4inch gun mounted astern and several machine guns but when firing commenced, around 0855, she put up a spirited defence. She scored several hits on Stier, damaging her engines and steering gear. However, overwhelmed by fire from Stier, the Hopkins drifted away; by 10 am she had sunk. Forty-two of her crew were killed in the action, and three more died later; the 16 survivors finally reached Brazil 31 days later.
Meanwhile Stier had been fatally damaged; unable to make headway, and not responding to the helm, Gerlach made the decision to abandon ship and scuttle her. She sank at 11.40 am. All but 2 of her crew survived; they were rescued by the supply ship Tannenfels, which was accompanying Stier at the time of the action.
Stier was originally built for the Atlas Levant Line, converted for raiding and sailed on 12th May 1942 for a voyage that was to last 139 days