Sebastian Aho pushed the lead to 3-1 at 14:32 of the third period. Brock McGinn scored an empty-net goal at 17:50 to make it 4-1.
"Just not really our best game," Capitals forward Lars Eller said. "I still feel we had another gear or two that we didn't show."
Darling made three saves on Nicklas Backstrom late in the second period to keep the Hurricanes ahead 2-1, and one on a Jakub Vrana breakaway at 6:14 of the third period. Darling, who entered with an .886 save percentage, also stopped Dmitry Orlov on a backhand in tight at 14:21, and Aho scored 11 seconds later.
"It's been an adjustment all year long with that, not getting the shots, especially like the [flutter] shots, but still getting the Grade A chances," Darling said. "It's been a big transition for me."