Joe Simpson’s Pilgrims twice led – through Josh Davenport and Will Pettitt – but were pegged back by a resilient Alfreton side.
The Reds’ goals were scored by Patrick Stefaniak, Henrick Craven and Kaigh Spencer.
Boston: Daniel Martin, Finley Hipkin, Finley Mackey (Alex Van-Tam 82), Toby Cotton, Dominic Chew (Leon Hagger 80), Joel Smith, Zac Hardy, Charles Doble (Kye Rook 72), Josh Davenport (Bradley Mindham 35), Jesse Ward, Will Pettitt. Sub (not used): Austin Barker (gk).
Referee: Alistair Wilson.