On 16 April, "Willis" cleared Melville as part of TG 22.3 to conduct hunter-killer operations-known as Operation "Teardrop"-on "barrier patrol" to prevent the penetration of U-boats to the east coast of the United States. Four days out of Melville, TG 22.3 rendezvoused with TG 22.4. At 0840 on 24 April, U-546 torpedoed and sank , one of the other escort destroyers in combined screen. A search immediately began; and a covey of escorts flushed out the enemy submersible and sank her in a determined attack.