Hearts lost out 1-0 to Hamilton Academical at a sun-kissed New Douglas Park on Wednesday night.
The tight encounter looked to be heading to a stalemate until Accies' Grant Gillespie headed the winner in the final minute of play.
Head coach Robbie Neilson fielded a strong starting line-up, with new signings Neil Alexander, Alim Ozturk, Morgaro Gomis and James Keatings making their Hearts debuts on Scottish soil.
The home side were first to threaten after two minutes. Accies' Andy Ryan dragged an effort wide from the edge of the six-yard box following a neat one-two with Ali Crawford.
Both teams attempted to play passing football with Hearts moving the ball out from the back, save for a few pinpoint long-range balls courtesy of Ozturk.
Accies found themselves with a half chance on the 20th minute mark after Jason Scotland picked the pocket of Sam Nicholson inside the Hearts half, but the Trinidad & Tobago striker blasted over the bar from 18 yards.
Five minutes later, and for the second time in the match, Crawford slipped in Ryan, but his tame shot was easily gathered by Alexander at close range.
Hearts then went close twice in the space of a minute. Jamie Walker rattled the underside of the crossbar from 25-yards out with a spectacular thunderbolt, before Dale Carrick's glancing header from a Nicholson free-kick made Michael McGovern work to tip the ball over the bar.
McGovern pulled off another impressive save after 36 minutes. Nicholson's defence-splitting pass was latched onto by Walker, but his angled shot was blocked by the Accies 'keeper at his right-hand post.
The Jambos started the second half unchanged, while the home side made wholesale subs. Walker threatened the home defence with a mazy run, making it as far as inside the box but his low shot was stopped with little effort from McGovern.
Hearts made their own raft of substitutions midway through the second half and Angus Beith's dead-ball deliveries proved problematic for the Accies defence. Just before the 70th minute mark, Nicholson fed Beith who strode into the box, but his inviting ball across the face of goal couldn't find a blue and white shirt.
With five minutes remaining, Gary Oliver did well to weave into the Accies box before seeing his effort blocked, the ball fell to David Smith but he drilled his shot wide of the left-hand post from 18 yards.
In comical fashion, Hearts almost grabbed the winner moments later when an Accies back-pass was completely missed by the trialist goalkeeper, but luckily for the home side the ball landed the wrong side of the post despite Scott Robinson's best efforts to charge it down and tap it in.
Just when it looked like honours would be even, Hamilton took the lead in the 90th minute. A cross from the left was nodded home by Gillespie, who rose to meet the ball unchallenged inside the six-yard box.