Paul McMullan scored with almost the last kick of the game as Dundee United stormed back to beat St Johnstone’s youngsters.
The Perth side took the lead against the run of play on 21 minutes thanks to striker Callum Hendry’s powerful header.
The 20-year-old son of former Scotland captain Colin added his team’s second in the 58th minute with a perfectly-placed curling shot.
United dug deep, though, and Logan Chalmers got one back on 64 minutes when he shot high into the visitors’ net.
With the momentum going their way now, a flowing move involving McMullan and Matty Smith was finished off by the former to make it 2-2.
The stage was then cleared for McMullan to score a brilliant solo effort two minutes into stoppage time added on.
With both club managers, Csaba Laszlo and Tommy Wright, watching from the stand, Craig Easton was in the United dugout and Alan Maybury was in charge of the visitors.
United’s captain for the night was Scott Allardice, who slotted in at centre-back. He was one of five Tangerines to have featured in the first team already this season.
Saints welcomed back Joe Shaughnessy, who skippered the Perth youngsters on his comeback from a leg injury suffered while cycling.
There was an early injury blow for the home side when Archie Thomas fell to the floor clutching his leg and he was replaced by Mati Zata after just six minutes.
The hosts had done most of the early pressing but they fell behind to a well-worked goal on 21 minutes.
A corner, which came gift-wrapped from United, was fired over from the right by Kyle McLean and Hendry rose to send a downward header past keeper Benjamin Siegrist.
Louis Appere tried to hit back for the home team when McMullan’s cross made its way to him but the sting was taken out of his shot.
Hendry was the dangerman up at the other end and he fired a 20-yard strike inches wide on 28 minutes.
United midfielder Declan Glass showed some fancy footwork inside the area to create space for himself in 39 minutes but his shot was well saved by Ross Sinclair.
It was almost 2-0 Saints three minutes from the interval when full-back Ciaran Brian curled a shot goalwards only for Siegrist to push the ball around the post.
The second half took a while to catch fire but when it did Saints grabbed their second.
There were 58 minutes on the clock when they worked the ball up the right to Ali McCann, who pinged the ball across the United box to the waiting Hendry. The frontman took a touch before sweeping a cracker of a strike into the postage stamp corner of the Tangerines’ net.
Just six minutes later, though, United grabbed a goal back.
It was a fine finish from Chalmers, who blasted the ball high into the St Johnstone net after it bounced in front of him inside the box.
The equaliser came on 78 minutes when McMullan won the ball, played a one-two with Smith then slid the return pass beyond goalie Sinclair from seven yards.
Smith headed the ball into the goalie’s arms with just a couple of minutes left and then hung back to steal possession off the day-dreaming Sinclair only to be smothered by the keeper. It looked like a clear foul but referee Colin Steven gave nothing.
United would not be denied, however, and McMullan raced up the park before beating Sinclair with a superb low shot.
Dundee United: Siegrist, Wardrop, Graham, Thomas (Zata 6), Bollan, Allardice, McMullan, Glass, Smith, Chalmers, Appere. Subs not used: Donaldson, Reekie, Ward, Banks, Cooney, Meekinson.
St Johnstone Colts: Sinclair, Brian, Donald, Wilson, Shaughnessy, McCann, Ballantyne (MacKenzie 78), McLean, Hendry, Struthers (Hamilton 86), Northcroft. Subs not used: Wills, Finnie, Quigley, Robertson, Woolley.
Referee: Colin Steven.