A last-gasp try to Adam Clydsdale has put the Knights into the finals, ending the Dragons' tournament and sending Manly home winless with an amazing 20-17 win.
With the Knights needing a win to progress they almost got off to the perfect start but Dane Gagai dropped the ball over the line.
Despite the fact the match had just become a dead rubber for them, Manly still took the field with both their star halves and it almost paid dividends when Kieran Foran chipped through for Daly Cherry-Evans but the Knights were able to defuse the raid.
Instead first points came from ex-Cowboy Blake Leary, who was the beneficiary of a beautiful inside ball from Foran in front of the sticks to take Manly to a 7-0 lead.
The Knights hit back through Tyler Randell who showed pure strength to push over out wide and then, after the half-time siren had sounded, Tyrone Roberts showed startling reflexes to latch on to an attempted Tony Satini chip from point-blank range and run unimpeded to the line to give Newcastle an unexpected 8-7 half-time lead.
When Feleti Mateo fluffed the restart to give the Knights a set at the line, Roberts produced an inside ball to Korbin Sims, whose flat pass allowed Sione Mata'utia to charge over.
Prize playmaker Cherry-Evans was hooked with five minutes to go after copping a pair of heavy knocks, with Manly deciding enough was enough with their marquee man.
A Mateo round-the-back offload that had to be seen to be believed (and even then was unbelievable) sent Brayden Wiliame on a free run to the line to close the gap to 14-13 with three minutes to play – even though it looked like Wiliame lost the ball in a tackle in the in-goal while trying to improve the position rather than grounding it.
The decision to award the try became a crucial call when Clint Gutherson went over shortly after to put the Sea Eagles up 17-14.
But with a spot in the finals on offer and the clock winding down, a stunning swerving solo run from Adam Clydsdale regained the lead for Newcastle in the final 30 seconds, sending the unlucky Dragons packing despite their earlier win over Parramatta and putting the Knights and Eels through to the knockout stages.