In a close knit affair at Craven Park, Hull Kingston Rovers grabbed another invaluable two points in their quest for a top six finish.
Rovers took time to get into the game early on, and this showed when Michael Worrincy crossed for the visitors after just 19 minutes.
But Rovers, fielding two debutants in their squad in the shape of youngster Liam Watts, and Australian Michael Dobson, a face well-known for helping Wigan's survival campaign in the 2006 Super League season, came back strongly thanks to some good forward play.
It was Dobson who grabbed Rovers' equalising try, when his inventiveness paid off allowing him to spin and crash over.
Liam Watts continued to be a nuisance with some strong forward runs, and impressive offloading with some ease, demonstrating maturity above his age of 17.
However, Rovers failed to take chances as they continued to dominate, and it was 'Quins who recovered the lead shortly before half-time.
Jon Grayshon finished off some good work from his team-mates, however, Harlequins missed their second attempted conversion in the blustery conditions.
But after half-time it was KR who took the game by the throat, running in 18 points, while keeping the opposition scoreless.
Chris Chester scored virtually straight from the kick off, with KR using their set of six effectively, following up from some great break away play.
Nineteen minutes later and Papua New Guinean Stanley Gene crossed for another try, slicing through the Quins defence.
Paul Cooke converted both to give the home side an eight-point lead.
But Quins' mistakes cost them, and it was thanks to the brilliant work ethic of the KR pack, including Watts' offload, that set up Dobson for his second.
Watts bounded through the defence finding space for his teammates to pass to Dobson, who crossed underneath the sticks. Cooke converted.
Harlequins continued to push in the closing few minutes for some sort of consolation, but it was not to be, with KR running out victors.
Match Details:
Hull KR
22T: Dobson (25,78), Chester (41), Gene (60)
G: Cooke (42,61,78)
Harlequins
8T: Worrincy(19), Grayshon (37)
HT: 4-8
Ref: S Ganson
Attendance: 8,084