Manager Nathan Jones made five changes from Saturday's defeat at Stoke, with Tom Ince and Adebayo made their respective first starts for the club after arriving on Deadline Day - and it was the latter, signed permanently from Walsall, who grabbed the second-half winner from the former's deft flick.
Joe Morrell and Ryan Tunnicliffe, who came on during Saturday’s match, were also in from the start, as were Martin Cranie and Kal Naismith as Jones refreshed his line-up.
Naismith and Kiernan Dewsbury-Hall combined to set Tunnicliffe up for the game's first shot at goal with less than two minutes on the clock. The midfielder would have dreamt about the chance to score against the club from whom he joined the Town in the summer of 2019, but his effort was well wide.
Town were attacking with freedom and Morrell was the next to have a go, after Ince had been wrestled to the ground on the edge of the box and Dewsbury-Hall's free-kick had come back off the wall. The Welsh international's 25-yarder was gathered by Lions keeper Bartosz Bialkowski at the second attempt though, as the Hatters' forwards prepared to pounce.
Adebayo was proving a threat both aerially and on the ground, but it was after he'd seen a shot blocked that Jordan Clark had the Town's best chance, chesting down Morrell's clip into the box and sending a volley on target, but Bialkowski was again in the right place.
Ben Thompson had the visitors' first effort of the game in the 37th minute, firing wide after Jed Wallace did well to whip in a cross from the right. Another chance came the midfielder's way two minutes later, but again he was off target from 18 yards.
Thompson was on the end of a late challenge by his former team-mate Tunnicliffe, who became the first player to be shown a yellow card by referee Graham Scott five minutes after half-time.
Then Ince brought the best out of Bialkowski, the former Ipswich keeper having to tip over the Stoke loanee's left-footed shot after terrific build-up play involving Cranie, Adebayo - who was fouled from behind laying it off for Tunnicliffe - Dewsbury-Hall and Naismith took the Hatters from one end of the pitch to the other.
The breakthrough came a minute later, in the 55th, and it was Adebayo who placed his left-footed shot low through the defender's legs and past Bialkowski after Ince had flicked Tunnicliffe's cross on.
Wallace bent one just over moments later as Millwall looked to hit back, but Adebayo might have had a second on 63 minutes when Clark stood a lovely cross up to the far post, only for the ex-Walsall man to head over the bar.
Morrell was withdrawn a minute later, having worked tirelessly during an impressive return to the side, with Rea coming on in his place. Within seconds Naismith fancied his chances from full 35 yards, but his volley nestled high in the Kenny End.
Sluga did well to claw a Scott Malone cross onto his cross bar, and then behind, when the left-back's deep centre looked like it was heading into the top corner.
The Croatian keeper raced off his line to deny sub Mason Bennett, after the Lions forward appeared to trip Clark as he raced onto the ball in the Town box, before flying across it to push Wallace's 20-yard free-kick around the post immediately afterwards. He completed the hat-trick by punching the resulting corner clear from right under his bar, under heavy pressure from the Millwall attack.
Millwall grabbed a 95th-minute equaliser when George Evans nodded in from close range. With seconds left on the clock, the ball was crossed towards Matt Smith, who headed across goal to George Evans and he prodded the ball beyond Sluga.
It was a tough blow for the Hatters, who will look to claim all three points when they welcome Sheffield Wednesday to Kenilworth Road on Saturday.
Town: Sluga; Cranie, Bradley (C), Potts, Naismith; Tunnicliffe (Berry 83), Morrell (Rea 64), Dewsbury-Hall (Cornick 83); Ince (Mpanzu 76), Clark, Adebayo (Collins 84).
Subs not used: Shea, Hylton, Moncur, Bree
Goals: Adebayo (55)
Yellows: Tunnicliffe, Sluga
Millwall: Bialkowski; Romeo, Hutchinson, Pearson, Malone; Thompson (Bennett 61), Bodvarsson (Burey 75), Woods (Williams 75), Evans, Wallace, Bradshaw (Smith 61)
Subs not used: Fielding, Tiensia, McNamara, Mitchell, Ferguson.
Goals: Evans (90+5)
Referee: Graham Scott
