St. Louis won 3-0 as rookie pitcher Shelby Miller pitched a complete game, retiring 27 straight after a leadoff single by Eric Young Jr.
The Blues scored late in the third period to tie the game, but the Kings won in overtime.
Jeremy Guthrie (5-0) allowed one earned run, seven hits and three walks in six innings to lower his ERA to 2.28.
With three straight victories heading into Game 6 on Friday night, the defending Stanley Cup champion Kings are on the brink of a remarkable comeback to knock out the Blues.
The Orioles escaped with a 5-3 victory Wednesday night despite allowing two home runs and getting only five hits.
St. Louis is now 5-1 in its last six games and 14-7 on the road.
Jeremy Guthrie lost 60 games over a four-year stretch with the Orioles before being traded to Colorado in February 2012. Now he's back in Baltimore for the first time, poised to face his former team Thursday night as a member of the Kansas City Royals.
Matt Wieters drove in three runs, including the tiebreaker in the eighth inning, and the Orioles beat the Kansas City Royals 4-3 Tuesday night on a soggy night at Camden Yards.
The Cubs ended the Cardinals' six-game winning streak Tuesday night, which was their longest since an eight-game run July 11-21, 2010.
The Blues have a day to reboot the system and still have home-ice advantage, by virtue of finishing a single point ahead of the Kings for the fourth seed in the Western Conference.
The Los Angeles Kings evened their first-round series with the St. Louis Blues at two games apiece with a 4-3 victory that included two third period goals Monday night.
Chicago's Jordan Danks, a backup outfielder, atoned for his baserunning blunder in the ninth inning by hitting a solo home run in the 11th that lifted the Chicago White Sox over the Kansas City Royals 2-1 on Monday.
The Kansas City Royals, saved when Billy Butler sent the game into extra innings, rallied past the Chicago White Sox 6-5.
Jonathan Quick made 30 saves in his fifth career playoff shutout, leading the Los Angeles Kings to a 1-0 victory over St. Louis on Saturday night and trimming the Blues' series lead to 2-1.
It was the first time the Cardinals have four in a row from the Brewers, who moved to the NL and have been in the Cardinals' division since the 1998 season.
Guthrie ran his unbeaten streak to a club record 17 consecutive starts with a four-hitter in the Kansas City Royals' 2-0 victory over the Chicago White Sox on Saturday night.
Jon Jay homered and drove in the go-ahead run in the ninth and Allen Craig and Daniel Descalso each hit home runs to lead the Cardinals to a 7-6 win over the Milwaukee Brewers on Saturday.
Matt Holliday and Carlos Beltran homered and Shelby Miller pitched six strong innings to help the St. Louis Cardinals beat the Milwaukee Brewers 6-1 Friday night.
The Royals' game against the White Sox was postponed Friday due to freezing rain and will be made up Monday, when the teams were scheduled to have a day off and the forecast is much better.
The Blues' defenseman scored with 50.4 seconds remaining to give the Blues a 2-0 series lead over the defending champions.