After the Texans' third safety dropped a sure pick, Braman blocked a Pat McAfee punt, eventually spotted the ball, pulled it in and slid into the end zone before he was touched.
But the Colts got the ball back with 1:39 remaining, which was enough time for Demps to make another crucial error. T.Y. Hilton ran a deep route right at him, then cut inside and ran on by, pulling in a 61-yard touchdown pass lofted up by Andrew Luck.
That made it 20-10 in favor of the Texans at the end of an eventful first half.
J.J. Watt was absolutely electric, with two sacks and a couple of tackles for loss against the Colts' overmatched offensive line.
The Colts have come back from plenty of second-half deficits before.
Not many of those comebacks have come against a defense with a stud like Watt wreaking havoc up front.
Indianapolis will get the ball to start the second half with a chance to make it a one-score game.