Lewis Alessandra netted his fourth goal in four games as Plymouth moved back into the top seven with a 2-0 home win over Northampton.Striker Alessandra was coolness personified as he rounded keeper Matt Duke and a defender to slot home following Drew Talbot's unselfish pass on 86 minutes. Irishman Anthony O'Connor's thumping 18-yard right-footed strike put Plymouth ahead after 28 minutes as Northampton failed to clear their lines. It was the defensive midfielder's first senior goal and a cracking one to open his account. A minute earlier both sides missed golden opportunities to open the scoring. Darren Carter's angled cross-cum-shot cried out from a touch to beat home keeper Luke McCormick but Cobblers striker James Gray could not apply the finish as he slid in. Plymouth countered immediately with the ball sitting up for Alessandra as everyone looked for an offside flag. Alessandra was unable to lift the ball over Duke, who was able to make an easy save. Ricky Holmes skimmed a shot from the edge of the box just over at the end of the first half and Northampton continued to press for a leveller early in the second, to no avail.