An initially tame League One contest burst into life on Saturday with three goals in a five-minute spell as the half-hour approached.
Ryan Gilligan had the freedom of Vale Park to net Town's 25th-minute opener and Andy Holt buried a thumping header from Jason Crowe's cross to double the lead two minutes later.
But Vale pulled one back as former Northampton man Marc Richards pounced on Mark Bunn's parry from Danny Whitaker's shot and the home side twice went agonisingly close to an equaliser before-half time.
Luke Prosser's header was cleared off the line before Richards nodded against the crossbar, both from right-wing corners by Paul Harsley.
Vale continued to pile forward on the resumption and deservedly levelled in the 49th minute when Danny Glover drove his first senior goal after latching onto a Richards flick.