Wisbech led three times but ultimately paid for defensive lapses and slumped to defeat at Fountain Fresh Park this afternoon.
The Fenmen held the upper hand for much of the first half and deservedly took the lead after 24 minutes when Toby Allen's left-foot strike beat the visiting goalkeeper.
There followed a hectic five minutes before the interval. Harry Twite headed a cross into his own net for the equaliser, then skipper Max Mattless restored the Fenmen's lead from close range after a goalmouth scramble.
But the visitors replied almost immediately through Mitchell, making it all square at the interval.
After the break Wisbech looked more likely to break the deadlock and the goal eventually arrived after 64 minutes. Man-of-the-match Allen was fouled in the box and he struck the resulting penalty hard and low into the corner of the net for his 18th goal of the season..
But a crazy five minutes turned the game on its head as the Wisbech defence fell apart. The danger came from the right wing and two crosses allowed Mitchell and Grist to give Mansfield the advantage.
The home side tried desperately to salvage a point and substitute Harley Murkin had the best chance, but his close-range header was straight at the goalkeeper.
A disappointing result for the Fenmen after last week's encouraging performance.

Wisbech: George, Howe, Kacirek, Twite, Mattless (c), Reed, Ward, Wilson, Allen, Grigas, A Williams. Subs used: Murkin, Hall, Conyard. Unused: Thompson.

Wisbech MoM: Toby Allen.

Attendance: 187.