The seventh-round pick from Harvard stayed calm by thinking back to his freshman year and first college start when he rallied the Crimson from a 21-0 halftime deficit for a 31-21 win over Dartmouth. At the time it was the biggest comeback in Harvard's 128-year history.
"I was actually thinking about that game," Fitzpatrick said. "The biggest thing when you're in those situations is you need to get everyone around you fired up."
Houston (1-10) got the ball first in overtime but had to punt it away when David Carr was sacked on third down.
St. Louis (5-6) scored 10 points in the final 30 seconds of the game to force overtime.
"I knew there was no way we were going to lose that game," Fitzpatrick said. "You sort of get that feeling out there, of invincibility, with the way the offense was playing late and the way the defense really stepped up."
The Rams recovered from a horrible first half, with just 117 yards and six first downs, to gain 312 yards and 16 first downs in the second half.
Fitzpatrick proved an able replacement after backup Martin left late in the first quarter with a blow to the head. He was 19 of 30 for 310 yards and three touchdowns in three quarters, despite being sacked five times.
The Rams entered the game without starter Marc Bulger, who is out indefinitely with a shoulder injury.
Houston piled up 24 first half points but fell apart in the second half, only adding a field goal the rest of the game.
"I felt sick out there," said Texans center Steve McKinney. "I was so disgusted I wanted to throw up. We were squandering some opportunities and sure enough it came back to bite us. It's really hard to lose a game when you're up 10 points with 30 seconds to go -- but we did."
Carr threw for a season-high 293 yards and three first half touchdowns, but couldn't find the end zone after that.
Andre Johnson had 159 yards, also a season-high, and a touchdown. It was his first 100-yard game and first touchdown catch of the season.
Carr hadn't thrown more than one touchdown pass in a game in almost a year. So when he threw his third of the first half, a 10-yarder to Corey Bradford just before halftime, he was so jubilant that he chased Bradford down and wrapped him up before playfully tackling him in the end zone.
That jubilation was short-lived however as the Texans found a new way to lose this week, squandering their biggest lead of the season.
Early in the game Carr had his way with a secondary that was missing both its starting cornerbacks and its strong safety.
"It was a great win playing a rookie secondary, a rookie quarterback and a makeshift offensive line," interim coach Joe Vitt said. "It wasn't pretty, but we got it done."
Holt scored on a 19-yard touchdown pass in the third quarter and Steven Jackson got the Rams within seven points on a 1-yard run midway through the fourth.
Jackson finished with 25 carries for 110 yards, improving the Rams' record when having a 100-yard rusher to 38-0 since moving to St. Louis in 1995.
Holt finished with 10 receptions for 130 yards and Bruce had four receptions for 94 yards. A 20-yard reception by Bruce late in the second quarter made him the 11th player in NFL history to top 12,000 yards receiving.
Notes: The Texans' seven sacks were a team record. Linebacker Morlon Greenwood had two, a career high. ... Martin had blurred vision after being sacked by DaShon Polk. He made a quick trip to the hospital during the game and was scheduled to have more tests Nov. 28.