Callum Roberts struck from the spot to grab a draw for promotion-chasing Scunthorpe at Boston.
Neither side was able to take control during a goalless first half, Rory Watson saving well from Kieren Donnelly to snuff out Boston's best chance and Zak Mills alert enough to block the Iron's Joe Starbuck.
Graham Coughlan's Pilgrims broke the deadlock 10 minutes into the second period, Donnelly once again unable to beat Watson but this time leaving Lenell John-Lewis with a tap-in.
Substitute Ben Grist gave away a 77th-minute penalty after ending on the wrong end of a tussle with Danny Whitehall, leaving Roberts to step up to salvage a point from 12 yards.
Report supplied by PA Media.
