The Gators, who currently hold down first place (7-3-1) but have played four more games than the Cards, wasted little time catching the attention of their unbeaten opponents.
Jason Boudreau opened the scoring just 20 seconds in, with Kody Krystia pulling St Charles even later in the opening frame, jamming home a rebound on a breakaway chance from Riley Lafrançois.
The Gators took advantage of one of the rare power-play opportunities in this contest as Cory Hannon pulled the trigger with just 17 seconds remaining in the opening frame to give BAC their second lead of the night.
Again, the Cardinals fought back as Lafrançois netted his first of two goals for the winners. The see-saw trend would persist as Boudreau matched the two-goal effort of Lafrançois, scoring his second of the game with the Cards short-handed, the Gators finishing an impressive two for three on the power play.
With time running down, it was left to the Cardinals' leading scorer. Lafrançois evened things at 3-3 before finding linemate Joey Manitowabi on the doorstep of Gators' netminder Matt Rychlo for the game-winning goal.
While Rychlo finished with 19 saves, almost half came on either clear-cut breakaways or quality one-on-one chances as the young netminder did a nice job of keeping things close.
In the other game slated for Dec. 20, the Lockerby Vikings surprised a higher-ranked opponent for a second straight game, doubling the Macdonald-Cartier Panthères 4-2.
The Vikes also started quickly as both Kyler Dusick and Jacob Bates tallied before the contest was two minutes old.
Lockerby doubled their lead in the middle frame as Nick Quesnel scored with his team short-handed, with Mitch Mensour adding the final goal for the winners.
Macdonald-Cartier made things interesting in the second half of the third period, receiving goals from both Alex Leduc and Miguel Lefebvre in the final six minutes, cutting the margin in half.
Lockerby goalie Brody Spourdalakis turned aside 20 shots between the pipes for the win, just one week after enjoying a solid outing as the Vikings upset Bishop Carter.
The double-header at the Gerry McCrory Countryside Sports Complex wraps up the first half of the schedule for the high school boys, with action resuming on Jan. 7 as Lockerby and Lo-Ellen go toe to toe.