Billy McKay scored the only goal as Inverness kept their hopes of avoiding relegation from the cinch Championship alive with a slender 1-0 win over Montrose.McKay struck just before the hour mark of Saturday’s play-off semi-final second leg at the Caledonian Stadium to finally see off the stubborn League One side after a goalless draw on Tuesday.Montrose’s hopes of staging a late fightback were hampered when Blair Lyons was sent off six minutes from time and Thistle will now face Hamilton in the final.Lyons thought he had scored in the first half, but his effort was ruled out for offside before Cameron Harper hit a post for the hosts.McKay broke the deadlock when he turned in following a corner and Thistle held on after Lyons was dismissed following a clash with Morgan Boyes.