At 09.32 hours on 20 Sep 1943, U-238 (Hepp) fired four torpedoes at convoy ON-202 and reported two hits on the ships in station #11 and #21. The Frederick Douglass in station #11 was damaged and the Theodore Dwight Weld in station #21 was sunk.

The Frederick Douglass (Master Adrian Richardson) was struck by one torpedo on the port side bulkhead between the #4 and the #5 holds. The explosion made only a relatively small hole in the side but blew off the hatch covers and strongbacks. The ship began to settle slowly. About seven minutes after the explosion and without orders, some of the eight officers, 32 men, 29 armed guards (the ship was armed with one 5in and nine 20mm guns) and one woman stowaway abandoned ship in two lifeboats. As the engine room was flooded five hours after the attack, the remaining men left the ship in the remaining two lifeboats. All hands were picked up by the British rescue ship Rathlin and landed in Halifax on 28 September.

At 21.56 hours the same day, the drifting Fredrick Douglass was sunk by two coups de grâce by U-645.