Step forward Charlie Connolly, on the end of a dummy offload from Thom Smith, to race across the line and dot down.
The last gasp try gave Doncaster a 33-30 victory which, allied with Ealing Trailfinders’ surprise defeat at home to Bedford Blues, sent them back to the top of the RFU Championship.
Knights have played two games more than their much wealthier promotion rivals but, with four fixtures left to play, Doncaster head coach Steve Boden will take this position.
He might not have been thrilled with the performance though, even if the spirit and the manner of their comeback showed his side’s strengths.
It was an error-strewn first half for the travelling side as the Knights scored two tries to Richmond’s three, Boden’s men appearing to have underestimated how physical they would need to be to keep the hosts at bay.
Maliq Holden and Connor Edwards scored the Knights’ opening two tries but they trailed 22-12 at the break.
That became 27-12 to Richmond before Connolly found himself at the bottom of the maul with the ball in his hands and a try on the board.
Sam Olver slotted his second conversion of the day before Kyle Evans danced over for Doncaster’s bonus-point clinching fourth try.
A one-point game became four when Richmond kicked a penalty on 76 minutes, forcing Doncaster to require a try to win the match. Connolly obliged on 82 minutes with Olver adding the extras.
It was Doncaster’s only lead of the game, but it was an important one.