Great Britain's Tom Aggar finished fourth in the AS men's single sculls final after losing his Paralympic title to China's Cheng Huang.
Aggar, the four-time world champion, had been unbeaten in a British vest since 2007 but that proud record was broken at Eton Dorney.
Cheng, who smashed Aggar's world record in Friday's heat, won Paralympic gold in his first year of international competition.
Australia's Erik Hollie finished strongly to win silver and Russia's Aleksey Chuvashev took the bronze, leaving Aggar empty handed.
No rival had ever previously got to within two seconds of Aggar in a head-to-head race through a dominant career in the arms and shoulders classification, dating back to his World Championship triumph in 2007, but he was up against it from the outset here.
Huang and Chuvashev both went faster than Aggar's old world record in the heat and it was they who set the early pace.
Aggar kept himself in touch at the halfway mark but slipped back as Horrie put in a strong second 500 metres to claim silver.
"I am absolutely devastated," Aggar said. "It's hard for me to describe. I am devastated it wasn't my day. I went out hard to lead from the front and get control.
"The two guys to the left of me were really fast. When I tried to dig deep there was nothing there."
Nick Beighton and Samantha Scowen, who only came together in the TA mixed double sculls last year, also finished fourth in their final after being edged out of the medals in a thrilling sprint for the line.