Hamilton Accies have work to do to avoid relegation to League One after Wasps boss Brian Rice stung his old side in the first leg of the Championship play-off semi-finals.
Luke Donnelly climbed off the bench for stricken team-mate Adam King to give Alloa the advantage in a tense tie at the Indodrill.
King collapsed off the ball midway through the first half and the game was halted for five minutes as he received medical treatment on the pitch.
The 27-year-old's plight caused concerned silence all around the Indordrill and Accies boss John Rankin screamed for the player to receive medical assistance, which quickly came.
It transpired the midfielder had suffered a delayed reaction to a head knock and, thankfully, was conscious and talking post-match.
Donnelly was his replacement after 25 minutes and that proved pivotal in the tie as the ex-Celtic youth slotted home in first half stoppage time when he got the break of the ball inside the box.
The sides go again on Saturday in the second leg at New Douglas Park, where the winners will meet either Airdrieonians or Falkirk in the final.
Accies announced an emergency loan signing just before kick-off, as Hearts yougster Liam McFarlane came in following the news first choice keeper Ryan Fulton has been ruled out for at least a week with a quad injury.
That led to Jamie Smith getting the nod in goal in one of three changes for Accies. Striker John-Pierre Tiehi also missed out through injury and was replaced by Dario Zanatta, while Steve Lawson dropped to the bench with Lewis Spence coming into the starting line-up. Dylan Stephenson was also absent through injury.
Inside the first 30 seconds Reegan Mimnaugh displayed Hamilton's intent as he opened fire from distance and his effort flashed wide. Moments later, the ball then broke to Andy Winter inside the box and his acrobatic effort was comfortably stopped by Jay Hogarth in the Wasps' goal amid a lively start.
The early onslaught continued with Reaghan Tumilty cutting in and testing Hogarth with barely five minutes on the clock.
Ex-Accies defender George Stanger had the ball in the net for Alloa after seven minutes, but he was deemed to have fouled Jamie Smith in the process, heading the ball out of the keeper's hands.
A defence-splitting pass from Spence after 13 minutes sent Zanatta in on goal and when his effort was turned behind from a corner, Fergus Owens had a great chance from the resulting set-piece when peeled off his marker at the back post. His downward header, however, was off target.
The game was halted for five minutes midway through the half after Alloa defender Adam King collapsed to the ground off the ball. It sparked major concern for his welfare around the Indodrill and Accies boss John Rankin immediately screamed for medical assistance for the stricken defender. Thankfully, the 27-year-old former Dundee United man was conscious and talking briefly to his gaffer Brian Rice as he left the field on a stretcher.
Donnelly replaced King and came close to opening the scoring within moments of coming on when his looping header towards the far corner was plucked out of the air by Jamie Smith.
Accies spurned a big chance when O'Reilly headed the back across goal for Zanatta, who couldn't direct a close range header on target.
And for all of Hamilton's chances, it was the Wasps who were buzzing by the break after Donnelly broke the deadlock in first half stoppage time. The ball fell to Donnelly somewhat fortuitously inside the box but he made no mistake with his finish as he found the bottom corner with a low strike.
Six minutes into the second half, Zanatta teed up Connor Smith just inside the box and the Hearts loanee dragged his shot agonisingly wide of Hogarth's far post as another Accies chance went abegging.
Quinn Coulson's goalbound effort was turned away by the head of O'Reilly after 58 minutes as Alloa threatened to double their lead and give Accies a mountain to climb.
In 75 minutes Coulson came so close again to making it 2-0 when he went on a mazy solo run before hammering a strike off the bar just inside the box.
Connor Sammon then scooped a glorious chance over the top that could have had Alloa really in control, but Accies are still in the tie going into the second leg.
ALLOA: Hogarth, Stanger, Taggart, Devine, Miller, King (Donnelly 25), Cawley, Strachan (O'Donnell 71), Maciver, Coulson, Sammon (Buchannan 86).
Scorers: Donnelly 45+2
Bookings: Miller
Subs not used: Muir, Graham, Rankin, Cannon.
HAMILTON: J Smith, Owens, O'Reilly, McGowan, Tumilty (Lawson 63), Mimnaugh, C Smith, Martin, Spence (L Smith 72), Winter (One 86), Zanatta (de Bolle 71).
Scorers:
Bookings: O'Reilly
Subs not used:- McFarlane, Easton, Sparrow, Morgan, Ashley-Seal.
HT: 1-0
Ref: Greg Aitken
Follow Lanarkshire Live Sport on Twitter via @LanLiveSport, like us on Facebook or find us on Instagram for the latest sports news, pictures and video.
