Two two-goal wins had put KooKoo in control of the series, but a 4-2 win last time out and tonight's shutout success has seen SaiPa completely change the dynamic of the best-of-seven showdown.
It took the home side time to adjust the balance of power in game four - the first 20 minutes remained goalless despite both sides having a powerplay opportunity, though the signs were there for SaiPa, as they had 15 shots on goal to KooKoo's seven.
The opening period still had a strong bearing on the game, as with four seconds left, the visitors' Manu Makela was called for tripping.
Starting period two with an extra man allowed SaiPa to stretch the opponents defence, a key reason for Patrik Siikanen having time and space to score on the left wing after being picked out by Antti Kalapudas.
Siikanen was then called for high-sticking seconds later, but the Kouvola side failed to make an instant response, which was costly late in the period, when Samu Bau raced into the KooKoo zone and beat the goaltender at the near post to double the lead.
SaiPa went into defensive mode in the third period, as KooKoo mustered only seven attempts on goal and failed to find a way past Kari Piiroinen, who made 22 saves in all to complete a playoff shutout.
The Lappeenranta side then finished the game off with an empty-net goal from Henri Nikkanen in the final three minutes, as Kalapudas and Otto Kivenmaki earned a second assist each and SaiPa completed the 3-0 win. The series lead is on the line in game five in Kouvola on Saturday 25th.