Derry City slipped to their third successive Airtricity League defeat as Drogheda United came from behind to win at Hunky Dorys Park.
David McDaid put Derry ahead from a penalty on two minutes with Drogheda defender Alan McNally lucky to avoid a red card for his foul on the striker.
But after Derry dominated early on, Declan O'Brien levelled from the spot for Drogheda on 24 minutes.
McNally nodded Drogheda ahead on 42 minutes and it proved the winner.
Derry will regret not making their initial dominance pay.
After the early penalty, Derry had a great chance to extend their lead in the seventh minute but Marc Brolly attempted to square to McDaid instead of shooting himself and McNally got back to clear.
Against the run of play, Drogheda got on terms on 24 minutes with Shane McEleney adjudged to have fouled Ryan Brennan.
O'Brien hammered his penalty straight down the middle to beat Gerard Doherty as Derry's impressive early start was pegged back.
McDaid looked set to hammer Derry back into the lead on the half-hour only for controversial figure McNally to put in a superb tackle.
McNally then rubbed salt into Derry's wounds in the 42nd minute as he rose unmarked to head Brennan's corner past Doherty.
Drogheda almost extended their lead in the 60th minute as Doherty made a great pointblank save to deny Peter Hynes after O'Brien had headed against the crossbar.
With Derry making second-half changes, Mark Farren shot straight at keeper Gabriel Sava on 81 minutes when a pass to the unmarked Simon Madden might have been the better option.
Derry produced further late pressure but to no avail as Drogheda's win kept them second in the table but still six points behind Sligo after the leaders defeated Dundalk 3-0.
The Candystripes drop to seventh in the table after Cork City and Bohemians both won on Monday night.