Clark gave away a sloppy corner within the first two minutes but Harriers managed to clear the resulting flag-kick.
But Clark played a major role on five minutes, setting up an opening goal with a huge clearance.
Hadley raced onto the gigantic kick and headed the loose ball over the advancing Sheffield to send Harriers fans into raptures. Stewart Hadley
Wotton attempted to hook the ball off the line but he could only hit it into the roof of the net.
Hadley needed brief treatment after colliding with the keeper whilst scoring the goal.
Jabery was cautioned for a late challenge on Ducros on nine minutes.
Hadley came close to a second on 15 minutes when Sheffield saved at the second attempt after the Harriers forward flicked a Mackenzie pass goalwards.
Plymouth, who were threatening with their height in the box, had a goal disallowed on 18 minutes for offside with Elliott appearing to get the final touch.
Harriers scored a second on 21 minutes when a suicidal back-pass from league debutant Bance was seized upon by Ducros and the nippy forward unselfishly squared to Mackenzie to tap the ball into the net from 12 yards.
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