The striker broke away from the halfway line, skipped past defender Arron Downes and cheekily rolled the ball through the legs of goalkeeper Michael Poke for his first goal for Pools in his ninth game.
After losing to the then bottom placed team in League Two the previous week, Pools weren't going to make the same mistakes this time.
The Gulls lacked a threat up front and Pools controlled the game for long periods.
Visiting right-back Antony O’Connor drew a diving save from keeper Scott Flinders on 15 minutes, but Pools took the lead on 31 minutes.
Jack Barmby, who this week extened his loan from Manchester United, took the ball down in the penalty area under pressure, moved it onot his left foot, picked out the top corner and fired in from 14 yards in style.
In the run down to half-time, the Gulls did threaten, but Flinders was only troubled once, when he saved well from Elliott Benyon, was picked out by Enoch Showumni and fired at goal from close range.
Pools doubled the lead on 55 minutes, Barmby’s low corner was flicked in by top scorer Luke James at the near post for his 14th of the season.
And, on 64 minutes, Harewood completed a comfortable win to keep Pools within a shout of the play-offs.