Gagne/By S. Bradley

TAMPA — Oh those three-goal leads.

When the Bruins have one, you never know how the game’s going to end.

Well, not all the time, just in some of the most critical situations in the franchise’s recent history.

With a chance to take a 3-1 series lead back to Boston today, the Bruins squandered a 3-0 lead for a 5-3 loss to the Lightning at the St. Pete Times Forum.

The series is tied 2-2 heading to the TD Garden, where Game 5 will be Monday night.

Simon Gagne, the scorer of the game-winning goal last spring for Philadelphia in the Flyers’ double 3-0 comeback, notched the go-ahead tally 6:54 into the third period.

Here’s a glance at the rest of the box score:

•Patrice Bergeron scored two goals and Michael Ryder added the third for the Bruins.

•Not to be outdone by Bergeron, Teddy Purcell scored twice for the Lightning. Sean Bergenheim added the tying goal and Martin St. Louis buried the empty-netter.

•Mike Smith came on in relief for Dwayne Roloson in the first period and finished the day with 21 saves on the same amount of shots.

•The Bruins’ first line of Milan Lucic, Nathan Horton and David Krejci combined for two shots on net, and Lucic’s giveaway at Boston’s blue line allowed Ryan Malone to set up Gagne’s game-winning goal.