The Pilgrims were dumped out by old foes Chorley following a cup classic under the floodlights at The Jakemans Stadium. United had twice led through James Clifton and Kabongo Tshimanga either side of half-time, only for Nick Haughton to take centre stage with a well-taken hat-trick.
Visiting skipper Andy Teague scored the Magpies' second equaliser and substitute Gregg Smith forced extra-time for the Pilgrims with a leveller of his own eight minutes from time. Matt Hughes saw red for the visitors in extra-time.