Boston United have a 1-0 deficit to overturn following the first leg of their Blue Square Bet North play-off semi-final with Guiseley.
Warren Peyton scored the only goal at Nethermoor Park with an unstoppable 35-yard free-kick 15 minutes from time.
Pilgrims caretaker-coach Jason Lee told BBC Lincolnshire: "We're disappointed but it was a fantastic strike.
"We were always in the game, we were competitive and weren't outplayed and we just can't wait for Sunday."
Boston went close through Jamie Yates and Spencer Weir-Daley and had a strong claim for a penalty for handball against Simon Ainge turned down, while Peyton hit the bar in the first half for the home side.
Lee added: "If we could have taken some of our chances early on, maybe things would have gone differently."
The second leg of the play-off semi-final is at York Street at 1500 BST on Sunday, 8 May.
The winners will face either Nuneaton Town or AFC Telford United, who drew 1-1 in the first leg of their semi-final, in the final the following Sunday.
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