There were only six points separating the sides as they went into the final six heats despite the Devils being without talented young Australians Brady Kurtz and Jack Holder.
They were in Denmark for the World under-21 team cup and Plymouth called up former Devil Ben Barker and Czech Republic star Matej Kus as guest replacements.
Carl Wilkinson of Scunthorpe also came in to replace in-form reserve Stefan Nielsen, who was on Elite League duty with Swindon in their match at Leicester.
Workington, who used rider replacement for the injured Rasmus Jensen, piled on the pressure with three maximum 5-1 heat wins in the last five races.
Todd Kurtz led the scoring for the Devils on eight points while former Plymouth rider Ricky Wells had a 15-point maximum for Workington. Adam Roynon, another former Devil, had ten (paid 12) points at reserve for the home side.
Plymouth continued their northern tour with a Premier League visit to Glasgow on Sunday afternoon (3pm) when Barker switched sides to make his final appearance for the Scottish Tigers before moving to Ipswich, another of his former clubs, where he replaces Lewis Kerr.
Workington: Ricky Wells 15 (5 rides), rider replacement for Rasmus Jensen, Kenneth Hansen 12 (5), Mason Campton 5+2 (4), Claus Vissing 11+3 (5). Reserves: Adam Roynon 10+2 (6), Matt Williamson 2 (5).
Plymouth: Ben Barker 6 (4), Kyle Newman 4+1 (4), Matej Kus 7 (4), Todd Kurtz 8 (5), Sam Simota 6 (5). Reserves: Carl Wilkinson 5+2 (5), Ellis Perks 1+1 (3).