Hull KR completed their third win in three meetings against St Helens this season with a 24-12 victory at Langtree Park to climb above cross-city rivals Hull into sixth place in Super League.
Saints had lost twice at Rovers in the league and cup this year but had won the last four home meetings against the Robins since 2009 and went into the clash on the back of impressive victories over Bradford and Salford.
But Rovers, who had Travis Burns and Mickey Paea sin-binned by referee Robert Hicks, outscored their opponents three tries to two, with Michael Dobson booting six goals from seven attempts.
Hull KR stunned their hosts by taking an eighth minute lead through a Burns try, after the Australian stand-off scythed through the defence and Newcastle Knights-bound Michael Dobson slotted over the conversion.
Then almost straight from the restart Burns burst through again with Greg Eden kicking ahead for Alex Brown to shrug off Francis Meli and go over in the corner to open up a 10-0 lead.
But Rovers had to manage without Burns for 10 minutes midway through the first half after he was sin-binned with Paul Wellens after a flare-up.
Wellens was furious with the decision and Saints' plight became worse when Eden scooped up a pass from Dobson to make it 16-0.
James Roby failed to find touch from a penalty just before the break to sum up the home side's frustration.
St Helens continued to make mistakes early in the second half but finally opened their account after 49 minutes when Francis Meli took Jonny Lomax's pass to cross in the corner and Gareth O'Brien landed the touchline conversion.
A Dobson penalty eased Rovers nerves to make it 18-6 after 55 minutes when Saints threatened a comeback.
Rovers had Paea, who this week agreed to join Hull next season, sin-binned on the hour for a professional foul but two more Dobson penalties stretched the advantage to 22-6.
Anthony Laffranchi did manage a converted touchdown for Saints six minutes from time but it was too late, with Dobson adding another penalty.