Aliaksei Protas scored twice and the Washington Capitals beat the Kings 3-1 on Sunday night.
Jakub Vrana also scored and former Kings forward Pierre-Luc Dubois had two assists en route to the win, which puts the Capitals back atop the Eastern Conference standings.
Logan Thompson made 25 saves to advance to 13-2-2.
Kevin Fiala scored for the Kings, who have dropped three of the last four and lost a back-to-back set for the first time this season. They finished 3-2-2 on their road trip, which began Dec. 10 with a win over the Islanders.
David Rittich made 18 saves in the loss, dropping to 10-8 on the season.
The Kings return from nearly a week off to host Edmonton on Saturday.
Going into Sunday, the Kings had the fifth-worst power play in the league and were 0 for 10 over the course of their lengthy road trip. They finally broke through thanks to Fiala, ending a six-game power-play scoring drought.
With Alex Ovechkin still working his way back from a broken leg, Protas has stepped up to fill the void on offense. With another multigoal outing, he matched the career high of 29 points he set last season in 45 fewer games.
After giving up a power-play goal early in the second, Washington responded with a goal of its own on the man advantage, as Vrana sniped home his sixth goal of the season to restore the lead for the Capitals.
Dubois continues to make a home for himself in D.C. as he extended his point streak to three games. He has points in seven of his last eight outings and leads Washington in scoring through the month of December.