George Ford's missed penalty proved costly as Stade Francais secured a dramatic 28-25 win over Bath to book a European Challenge Cup final spot.
Amid unsporting jeers at the Stade Jean Bouin in Paris, Ford – overlooked this week for Warren Gatland's British and Irish Lions squad – was wayward with a kick that would have levelled it up.
Todd Blackadder's side had staged a superb fightback to lead, having been 18-6 down with 17 minutes remaining, but Hugh Pyle's converted try and Jules Plisson's last-gasp drop goal turned the match back in the hosts' favour.
Stade, runners-up in 2011 and 2013, will now face Gloucester in next month's final at Murrayfield.
The home side saw Plisson's early penalty quickly cancelled out by Ford, but Geoffrey Doumayrou touched down in the corner 12 minutes in.
Another Ford three-pointer kept the visitors within touching distance at the break, but one-time Bath target Will Genia offloaded for Plisson to score early in the second half.
With Plisson adding the extras, Bath faced a 12-point deficit and saw Ford spurn a chance to cut the gap with an off-target penalty just before the hour.
But Blackadder's side refused to give in and Semesa Rokoduguni drove over the line before Ford rediscovered his accuracy to set up a grandstand final 15 minutes.
Robbie Fruean's try levelled it up and, although Ford missed the resulting kick, Elliott Stooke put the finishing touches on a fine team move and his try was converted.
Still the drama was not over, as Stade second-rower Pyle powered through and Plisson held his nerve to tie the scores.
Plisson's drop goal transpired to be the winner, but that was only confirmed after Ford had fluffed his lines.