Philip Lowry rescued Derry City from an embarrassing FAI Cup quarter-final exit with an 84th-minute equaliser.
The former Linfield man fired in the late leveller just as it seemed nine-man Drogheda were going to pull off a remarkable against-the-odds victory
Defender Ryan McBride volleyed Derry into a 13th-minute lead but Alan McNally forced in Drogheda's equaliser.
United had Peter McGlynn and Shane Grimes red-carded but Carl Walshe put United ahead on 51 minutes.
Drogheda actually finished with eight men as Gavan Holohan became the third man dismissed by referee Derek Tomney.
Holohan picked up a second yellow card just as the match was heading into five minutes of stoppage-time.
Drogheda held on for the 2-2 draw, meaning a replay at Derry's Brandywell ground on Tuesday night.
It was a massive relief for Derry as their season pretty much hinges on the League of Ireland's main cup competition.
Candystripes boss Peter Hutton had underlined just how much of a priority it was by fielding a vastly weakened team which lost 5-0 away to league leaders Dundalk on Monday night.
Hutton made nine changes as he fielded his strongest team against last year's beaten finalists.
Things looked to be going to plan for the visitors as McBride thumped in the opener, but poor marking from a set piece saw Drogheda central defender McNally head in the equaliser 10 minutes later.
McGlynn then had a shot blocked by Barry McNamee but the Drogheda defender became the first man sent-off for a rash challenge on Dean Jarvis on 33 minutes.
Early in the second half skipper Shane Grimes was the second man sent-off as he received a straight red for a comment to referee Tomney.
Incredibly, though, the nine men went into the lead in the 51st minute when Walshe scored with a header after Derry again failed to deal with a free into the box.
Time looked to be running out for Derry, but summer signing Lowry saved their season by shooting in the equaliser.
Then, to add to the drama, Holohan was sent-off for picking a second yellow card, apparently for kicking the ball away, to leave the hosts with just eight men on the pitch.
Derry tried to snatch victory but boss Hutton will be relieved to be getting a second chance against a Drogheda side who will have their three dismissed men suspended for the replay.