Carl Forber held his nerve to kick Workington Town into the Betfred League 1 play-off final after withstanding a Keighley Cougars comeback at Derwent Park.
Forber slotted a penalty in golden point extra time to secure an 18-16 victory and home advantage in the final.
Workington led by 10 points at the break but the Cougars clawed their way back into the match through a try from Charlie Graham, then Kyle Kesick went over with seconds remaining on the clock.
Jack Miller's conversion ensured extra-time but Workington held firm and took advantage of a penalty award to seal their place in the Grand Final.
Matty Beharrell starred for Doncaster in their 48-34 win over North Wales Crusaders at Colwyn Bay, but the hosts also staged a stirring comeback to leave the result in doubt.
Beharrell scored a try and eight conversions as the visitors twice led by 30 points, only for the home side to hit back with three tries in six minutes from Jordan Gibson, Ben Morris and Tom Johnson.
Gavin Rodden also went over to reduce the deficit to 12 points but Doncaster rallied and a late try from Jake Sweeting sealed their win.
