Sophie Wells won Great Britain's third equestrian medal of the Paralympics at Greenwich Park.
But the 22-year-old could not emulate her fellow Paralympic debutant Natasha Baker, who landed the Grade II individual title on Saturday, in taking gold.
Wells, from Newark in Nottinghamshire claimed silver behind Belgium's Michele George, a Grade IV result that was reversed from the 2010 World Equestrian Games in Kentucky.
Wells, who was born with amniotic band syndrome that affects her joints, is such an outstanding dressage talent that she has also competed at non-disabled international level. But a mistake midway through her test here on Pinnochio cost her dear as their score of 76.323% fell short of George's 77.065% aboard Rainman, with Dutch rider Frank Hosmar and Alphaville taking bronze.
Wells' display, though, tightened the British grip on team gold after they took a commanding lead into the final day of that competition.
Wells, whose test came immediately after George's, struggled to conceal her disappointment at not securing a Paralympic individual gold, although she will be a leading contender in Tuesday's freestyle to music class.
"If I hadn't had the mistake it might have been a different story," she said. "I knew I would have to do the best test I had ever done, but the Paralympics is when everyone is at their best.
"You can't afford a mistake, but unfortunately I had one and I take complete responsibility for that. The other bits in the test I was really pleased with. I tried to nail every movement, but we couldn't nail one of them and that was what lost it for us.
"Maybe the fact he (Pinocchio) is so big and powerful counted against me today. A simple change for us is not just stopping, I really have to drive him into it. It was the tiniest miscommunication. You do your best, and my best today wasn't good enough.
"I am disappointed. I knew I had blown it. But I know why I lost it, rather than not knowing why I lost it. We want to win, otherwise we wouldn't be here. But the horse has brought me a long way and I am pleased with him. These things happen."