Harriers slipped a miserable-looking seven points adrift of the play-off places as they suffered a first defeat under Gary Whild with a 1-0 set-back against Grimsby at Aggborough.
A strong atmosphere greeted the two teams and it was the visitors who strode forward with the most confidence early on; Ross Hannah firing over a free-kick from close range and Lanell John-Lewis denied by some brave goalkeeping by Danny Lewis
as the stopper dove at his feet to gather the ball.
Harriers etched out their first shot at goal on 18 minutes when Amari Morgan-Smith held the ball up out wide, awaiting the charging run of Michael Gash who powered into the area before arrowing a shot over James McKeown's bar.
Soon after, though, the Mariners had the lead and it came almost from nothing as Alex Rodman picked up the ball from distance and tried his luck with an ambitious chip that looped up and dipped beyond the grasp of Lewis before landing in his net.
On 26 minutes Harriers almost responded with an equaliser as Josh O'Keefe threaded Nick Wright through on goal, though the forward's low shot was blocked excellently by McKeown - this before an AMS effort from close range blazed just wide.
It was easily the strongest spell of the game for the hosts and the chances continued; Wright crossing excellently for Amari'i Bell whose header was tipped on to the post before being gathered by McKeown, the goalkeeper then parrying away a Lee Vaughan
shot on the angle.
Early in the second half a Gash flick-header was held comfortably enough by McKeown, Vaughan again striking off target with a distance free-kick that drifted off target around the hour mark.
It was a good spell of pressure after the restart but while Harriers found some fine positions and won their share of free-kicks and corners, finding a way past the Mariners was proving difficult, with Adrian Cieslewicz hurled into the mix to try and make a difference.
With 68 minutes gone Josh O'Keefe almost found a leveller for his team as he absolutely leathered an effort at McKeown from a hefty distance - it dipped frantically and beat the goalkeeper but, unfortunately, also his target as it crashed just on top of the net.
Into the final dozen minutes or so, Harriers finally found a way beyond the Mariners back line, real bustle seeing the ball eventually fall to Cieslewicz who saw his goalbound shot blocked on the line.