Two Sisters. One road trip. What could possibly go wrong?

Lottie has always followed the rules, her life is comfortable and she is - finally, finally - marrying her long-term, sensible, boyfriend Dean.

Tina is carefree, wild and, maybe, just a little bit careless. She doesn't understand Lottie's obsession with settling down with 'dull Dean'. There's so much to explore in the world.

The two sisters have drifted apart since the death of their older sister. Without her, Lottie and Tina realise how little they know each other. Desperate to remedy this, Tina convinces Lottie to set out on a road trip across the US, just the two of them.

But Tina has one more surprise in mind to shake up Lottie's life - she must say yes to everything Tina suggests, no matter what . . .