At 21.18 hours on 29 Oct 1942 the unescorted Laplace (Master Alexander MacKellan) was hit on the port side in #1 hold by one torpedo from U-159 while steaming on a non-evasive course at 9 knots in fine weather about 350 miles south-southeast of Cape Agulhas, South Africa. The U-boat had already been chasing Ross when a column of smoke coming from Laplace was sighted and eventually managed to sink both, but had to ignore a third ship sighted during the chase of the second. The explosion blew the hatch covers off and scattered the derricks over the deck. The master ordered the engines to be stopped and the crew to lower the lifeboats and stand by after distress signals were sent as the ship began settling slowly by the head. At 21.55 hours, the U-boat fired a coup de grâce that was seen to miss the stern from the starboard side by the survivors. On sighting the torpedo track, the master left the ship as last man and when his lifeboat was about 150 feet away, a second coup de grâce struck on the starboard side in the engine room at 22.07 hours. The explosion broke the back of the Laplace and caused her to sink by the bow within three minutes.

The master, 55 crew members and five gunners (the ship was armed with one 4in and six machine guns) had abandoned ship in four lifeboats and were all rescued. The boats set sail after waiting for 17 hours at the sinking position and were separated the next night after they hove to due to increased wind and rough seas. The most survivors were eventually picked up by a SAAF crash boat and landed at Port Elizabeth. The 20 occupants in the boat in charge of the chief officer were picked up by the American Liberty ship George Gale and landed at Aden on 19 November. The master and ten other survivors were in boat equipped with a portable emergency transmitter that became wet during the abandonment and the first radio operator could not know if his distress signals were picked up as the receiver was out of order. He eventually managed to get into contact with a SAAF station in the morning on 2 November, but the wireless set broke down before the position could be repeated. At 17.30 hours on 2 November, the eleven occupants were picked up by the Porto Alegre (Master José Francisco Pinto de Medeiros) in position 37°06S/24°30E, which also hoisted their lifeboat aboard. However, it was secured on #2 hatch despite the suggestion of the master to rig a derrick to make it ready for lowering. About 24 hours later, the Brazilian ship was torpedoed and sunk by U-504 (Poske) and the survivors from Laplace abandoned ship again on a raft. They later transferred to a lifeboat and eventually made landfall together with the Brazilian survivors near Port Elizabeth on 7 November.