The Dynamo lost the first leg of their Western Conference Championship matchup, 2-0, at BBVA Compass Stadium.
The Sounders got off to a dream start when Gustav Svensson powered a header past Joe Willis following a Nicolas Lodeiro corner in the 11th minute to give Seattle a 1-0 lead and an important away goal.
Houston was then forced to play with 10 men after Jalil Anibaba's red card in the 28th minute.
Former Dynamo Will Bruin scored the go-ahead goal with a header in the 42nd minute to give the Sounders a commanding 2-0 aggregate lead in the championship.
Houston almost found a goal in the second half when Mauro Manotas beat his defender and was in on goal only to fire his shot wide of the Seattle net.
Seattle will host Houston in the second leg at CenturyLink Field on Thursday, Nov. 30, to decide which team will represent the West in MLS Cup.
Houston will need to hold Seattle goal-less and also score three goals on the road to come back to win.
Information from ESPN was used in this report.
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