A 16th goal of the season from Marc Connolly gave 10-man Rhyl hope of progress to the final after they had trailed Connah's Quay 2-0 within the first 32 minutes.
Connolly struck a stunning 25-yard free-kick past Nomads' keeper Terry McCormick 10 minutes after the break, after the Lilywhites had turned-in a lacklustre first-half display.
Craig Jones put the hosts in front when keeper Paul Pritchard could only parry a free-kick and it got worse for the visitors when skipper George Horan, playing against his former club, was dismissed by referee Neil Morgan for a tackle on Andy Olsen.
Chris Herbert made no mistake from the resulting penalty, but Quay found it more difficult against 10 men and both Greg Stones and sub Lee Hunt could have levelled for Rhyl.
But Nomads missed the chance to restore their two-goal cushion ahead of the second leg at Belle Vue when Mike Hayes twice fired efforts wide.
Report and stats courtesy of welsh-premier.com