Bogey club Cornish Pirates launched a second half fightback to inflict back-to-back home defeats on Doncaster Knights.
Knights had hoped to go into the month-long British & Irish Cup break with four wins out five in the Championship.
But the Pirates - who make a habit of winning at Castle Park - had other ideas.
Mat Clark’s eighth minute try was converted by Dougie Flockhart, who then exchanged penalties with Kieron Hallett to take Knights into half time with a 10-3 lead.
But Pirates piled the pressure on at the start of the second half and quickfire tries from Tom Kessell and Matt Evans, both converted by Hallet, saw the visitors turn the game on its head.
Hallett then went over himself, and kicked the extras, to give Pirates breathing space before Latu Makaafi crossed for the hosts.
Knights set up a grandstand finale when Micheal Hills fought his way over and Flockhart converted but Clive Griffiths’ men had to settle for a losing bonus point.