(Michael Gash 83)
Michael Gash's late finish ensured the Boxing Day spoils went to King's Lynn.
Boston United - who lost skipper Luke Shiels to a straight red card after just 16 minutes at the Walks- battled to hold the National League North leaders until the 83rd-minute.
Seconds after Gash had put the Linnets in front the hosts had Ryan Jarvis dismissed, but by then the Pilgrims were left with too much to do.
With Alex Penny suffering a hamstring injury and Pierce Bird recalled by Notts County, Ben Middleton and Simon Ainge returned to United's defence, bringing experience but a lack of match fitness with just one start between them in the past eight matches.
Dayle Southwell was handed the first start of his loan spell and Brad Abbott returned from suspension, Dominic Knowles and Jonathan Wafula dropping to the bench.
United lost skipper Luke Shiels to a 16th-minute red card as he brought down Adam Marriott outside the Pilgrims' penalty area.
From the resultant free kick Aaron Jones forced a save from Peter Crook, who then denied Gash as he followed up.
As the leaders piled on the pressure, Crook then kept out Sam Kelly's effort.
But back came Boston, Tom Platt forcing Alex Street into a save.
Kelly began the second half by sending a long-ranger wide of the Boston upright before Jordan Thewlis couldn't get his effort on target at the other end.
Crook collcted Jones' 25-yard free kick before the same player aimed too high with another dead ball effort.
Marriott was the next Linnet to be denied by Crook.
For Boston, Thewlis' claims for handball after his effort was blocked by Kelly fell on deaf ears.
But Gash settled the contest in the leaders' favour in the 83rd minute, converting substitute Sonny Carey's cross-shot from close range after it deflected kindly.
Seconds later and Lynn were also down to 10 men as Jarvis was sent off for a foul on Jake Wright, who had replaced Thewlis.
LYNN: Street, Jones, Fox (Carey 65), Jarvis, Barrows (hawkins 80), McAuley, Kelly (Ward 86), Richards, Gash, Marriott, Henderson; Subs (not used): Payne, Stewart.
UNITED: Crook, Middleton, Whittle, Platt, Ainge, Shiels, Rollins, Abbott, Southwell, Thewlis (Wright 73), Woolford (Jackson 87); Subs (not used): Knowles, Wafula, Willis.
REF: Robert Massey-Ellis.
ATT: 2, 246.