Alex scored in second-half stoppage time to seal the win as the Fire (13-8-5) moved two points ahead of the Dynamo for third place in the Eastern Conference.
Brian Ching scored in the 90th minute for Houston (11-7-9), using his left knee to deflect Brad Davis’ corner kick into the net. The late goal spoiled Chicago goalkeeper Sean Johnson’s bid for a fifth shutout of the season. Johnson finished with five saves, including a difficult stop on Je-Vaughn Watson a minute earlier.
Nyarko picked off a pass intended for Dynamo defender Jermaine Taylor, ran 40 yards, and beat goalkeeper Tally Hall 50 seconds into the match. It was the second-fastest score of the year for Chicago. Dominic Oruro scored 25 seconds in against Toronto on April 21.
Houston forward Macoumba Kandji nearly scored on a Chicago defensive miscue in the 13th minute, but caromed the ball into the net with his right shoulder and was called for a hand-ball violation.
Paladini made it 2-0 when his right ankle deflected Sherjill MacDonald’s pass behind Hall from seven yards out six minutes later.
Alex got his first goal for the Fire on a 20-yard lob shot off the right post into the net about 3 minutes into stoppage time.