Milne’s yellow-card foul on Lewis Smith marked the first real crack in Hearts’ resistance. From the resulting free-kick, Stuart Armstrong whipped in a dangerous ball, Dan Happe nodded it back across goal, and both Kevin Nisbet and Lewis Mayo surged in to finish.
The goal was ultimately awarded to Mayo, and any Hearts hopes of a VAR rescue for an infringement were snuffed out.
Things deteriorated further for the visitors when Stuart Findlay brought down Toyosi Olusanya in the box, conceding a penalty and receiving a red card. Nisbet, denied the opener, made no mistake this time.
Vrancken now has to lift his squad for a daunting Europa League qualifier against Benfica, with the first leg in Lisbon on Thursday at 20:00 BST.
“We let it slip in five minutes,” the Belgian said afterward. He lamented a lack of game management—committing too many bodies forward instead of controlling transitions while 1-0 up—and stressed the need to reset quickly and be fully focused for the next match.