Promotion-chasing Plymouth suffered their second home Sky Bet League One defeat of the season after being beaten 2-0 by mid-table Lincoln at a sold-out Home Park.
Lincoln stunned their high-flying hosts via a lightning counter-attack on 28 minutes.
Imps goalkeeper Carl Rushworth started the move after collecting a corner and forward Olamide Shodipo finished it, tucking away Danny Mandroiu’s cross into the box, after being sent racing away by Lasse Sorensen.
Argyle suffered a further setback in the 47th minute as City extended their lead through Ben House, who held off central defender James Wilson before turning and letting fly past Greens goalkeeper Callum Burton from inside the box.
The hosts came close to an instant response but Jay Matete’s volley was turned over by defender Harry Boyes.
Argyle’s best first-half chance fell to top scorer Ryan Hardie, who raced clear to beat the offside trap but could not beat Rushworth at his near post.
As Argyle pressed forward, Burton made a superb 70th-minute save to deny City substitute striker Luke Plange.