'Greta' will remind you why you should never be kind to strangers.

“My friends say I’m like chewing gum. I tend to stick around.”

Those are the words 20-something Frances McCullen would later come to regret.

In the opening scenes of Greta, Frances (Chloë Grace Moretz) finds an abandoned green handbag sitting on a New York subway carriage, on the way home from her waitressing job.

Inside the handbag is a packet of pills, a lipstick, and an ID card for a woman named Greta Hideg.

Watch the trailer for Greta. Post continues after video…

Frances, who has only recently moved to the city from Boston, decides to return the handbag in person.

She arrives at the address listed on the card and Greta (Isabelle Huppert) answers the door. Greta is aged in her 60s, she has a French accent, and she seems only mildly surprised that a young woman would travel all the way to her apartment to return her handbag.

She immediately invites Frances in for a cup of coffee.

Greta’s apartment is cramped and worn. The focal point seems to be a large piano, which vibrates menacingly as a loud pounding sound comes from the wall behind it.

The eccentric piano teacher explains away the noise, telling Frances her neighbours are remodeling.

Over their hot cups of coffee, the unlikely pair strike up a friendship. Greta confides in Frances, telling her how lonely she's been since her only daughter moved to Paris.

Frances, who is still grieving for her late mother, sees something in Greta. A maternal presence that's missing in her life.

A few days later, Greta calls Frances and asks her to go with her to adopt a dog.

New to Manhattan, and used to small town hospitality, Greta agrees to accompany Frances to the dog shelter.

A couple of more outings follow.

It seems like the start of a lovely cross-generational friendship. It feels like these two relative strangers might actually be able to connect and find a sense of home in each other.

Then it happens.

Without giving too much away, the dynamic between Greta and Frances swiftly changes.

What follows is a series of unsettling events that slowly build until you're left asking "what the f**k?", "what the actual f**k?", and also "what the f**king f**k?".

To sum Greta up - not much happens and then everything happens.

Greta is an enjoyable ride and a very important lesson in stranger danger adults. You'll leave the cinema vowing to never help a stranger again.

And you'll never look at an abandoned handbag without a distinct chill running up your spine.