Last year's beaten finalist appeared to have thrown in the towel for the season following an underwhelming effort on Saturday.
The home side notched a 10-1 win but found the going much tougher in the return fixture yesterday, recording a 7-6 overtime victory.
The Admirals gave away the puck too easily on the Saturday but bounced back with a more determined effort. Their resolve, combined with some ill-discipline from the Thunder, meant game two went down to the wire.
The teams were tied 2-2 at the end of the first period, 3-3 in the second spell and 6-6 at the end of regulation time.
Canadian Hassan Saeed found the winner three minutes into overtime with a crisply-taken slap shot.
His team-mates did a great job setting a screen and he drilled the shot past the goaltender.
Earlier, French import Yvan Kerneis opened the scoring for the Thunder.
Matt Enright and Gino Heyd scored two goals apiece and Damian Watson also got his name on the scoreboard.
