A collision sent the ball spiralling over to Houston's Giles Barnes just inside the area. Barnes sent a sliding pass back to Will Bruin, whose shot deflected off Impact defender Eric Miller's foot and bounded over goalkeeper Troy Perkins.
That goal in the 40th minute was all the Dynamo needed to beat Montreal 1-0 on Saturday, and eclipsed an otherwise outstanding defensive effort by Miller in just his second MLS star.
"It was a block that just went over," Impact coach Frank Klopas said. "Nothing that you can do about that. We had numbers back and got the block, but it is what it is."
The Dynamo (2-0-0) scored four goals against the New England Revolution in last week's season opener. That prolific offence was nowhere to be seen on Saturday as the Impact tightened up on defence.
Miller and Hassoun Camara led a back line that pressed the Dynamo up high and kept scoring chances to a minimum.
"We knew they had a very strong attack," Camara said. "We wanted to press high and stay tight with our opponent. We made it tough for them by not giving them space. It was a good game, but in the end we are not happy because we lost on the unlucky goal."
Montreal's attempts to move the ball into the middle found stiff resistance from the Dynamo defence in the first half. Brad Davis and Kofi Sarkodi were particularly formidable as they defended on the crosses.
The Impact (0-2-0) turned up the attack as the second half opened. Patrice Bernier and Andrew Wenger were able to make more runs into the middle and numerous chances that failed to find the back of the net.
"We needed to push the game," Klopas said. "There was a sense of urgency and all the guys pushed to be quicker on the ball and switch the point of attack. We need to create enough chances and then finish them. I think they will come."
Bernier and Wenger worked well together in creating chances while also getting into position for passes from Hernan Bernadello and Felipe Martins.
Wenger and Bernier both had late shots that forced Dynamo keeper Tally Hall to make diving saves. A shot by Wenger in the 63rd got by Hall, but was cleared off the goal-line by Sarkodie.
"We created opportunities, but they dropped a lot of guys deep," Wenger said. "It was tricky for us. We played well overall and should have come away with a point, at least. I would have preferred to win ugly, but that's soccer."
Note to readers: This is a corrected story. A previous version stated Will Bruin in the 41st minute instead of the 40th.