The past has never seemed so inviting as it does in Colin Trevorrow’s DIY time-travel romance.

Like a low-key Back To The Future, this unexpected indie is propelled by a delicious premise, a classified ad that reads: “Wanted: Someone to go back in time with me.”

Advising any applicants to “bring your own weapons”, it also assures readers that “I have only done this once before.”

Jeff (Jake Johnson), a rather feckless journalist for a Seattle magazine, is assigned to investigate.

Along for the ride come two interns, Darius (Aubrey Plaza) and Arnau (Karan Soni), though it soon becomes clear that Jeff has more interest in the fact their journey takes them to the Washington town where his high school sweetheart still lives.

It’s left to Darius to trace the would-be time-traveller – who, it soon emerges, is a grocery store clerk named Kenneth (Mark Duplass).

Is he a nutjob or the sanest man around? Has he really ripped the fabric of the space-time continuum before?

Derek Connolly’s finely tuned script teases us with the answers throughout. While the film may lack Looper-style flourishes, there’s enough time-travel talk for brainiacs to chew over.

But Safety Not Guaranteed is not so much about the science of time travel as the emotion of it – why we feel the need to revisit the past.

Both funny and heartfelt, Trevorrow stops it from ever becoming too mawkish or melancholy.

What really impresses, however, are the performances. Mumblecore actor/director Duplass and Parks And Recreation star Plaza forge a tender bond, playing to the reality of the situation and never undermining their characters.

Best of all, it builds towards a quite marvellous ending that, even if it cost half the budget, was seriously worth it.

Verdict:

A smart character-driven charmer that gets better as it unfolds. Trevorrow and his excellent cast deserve to travel to the next level with this.