Paul McMullans late goal gave Dundee United a first-leg advantage over 10-man Inverness in the Scottish Premiership semi-final.
By then, Inverness had come close to an opener when Jordan White headed off the post then lost Liam Polworth to a red card for a high foot on Mark Connolly.
The eventual winner will play either Hamilton Academical or St Mirren – whichever side finishes second bottom of the top flight – in next weeks two-legged final.
Osman Sow came close to an early opener for the visitors, his left-footed low shot in the box saved by Inverness keeper Mark Ridgers, who was then tested by McMullan.
White had the hosts best chance when he nodded against the upright following a ball into the box from Joe Chalmers. He tried again before the break but this time his header was saved by United keeper Benjamin Siegrist.
Connolly, a former Ireland U21 international, joined Dundee from Crawley Town in January, having previously experienced Scottish football as club captain at Kilmarnock for the 2015/16 campaign.
United tried to make their numerical advantage could after Polworths dismissal early in the second period and eventually did with 12 minutes left.
Sows replacement Clark struck firmly against the right-hand post and McMullan converted off the opposite post.
Inverness CT manager John Robertson: “We dont feel its a red car. It could easily have sufficed with a yellow. For the referee to change the whole complexion of the game on that incident – we feel hard done by.
“I can understand why hes given it – we know the laws of the game. It is what it is. We are 1-0 down. Weve won at Tannadice before. We go down there full of confidence.”
Dundee United manager Robbie Neilson: “Pleased with tonight but by no means are we on easy street now. Weve got a tough, tough game coming up.
“The sending off has a bearing on the game. Ive been delighted with Paul McMullan since I came in. Hes got potential to really go far in the game because hes got that pace and hes got the fitness levels as well.”
The hosts resistance cracked with 12 minutes left after Liam Polworth was sent off but its all still to play for on Friday.