Ellen and Alexa have survived hangovers, dodgy landlords and most of their twenties together.

But can they survive this?

One Saturday morning, while nursing The Hangover from Hell, a flooded kitchen leads best mates Ellen and Alexa, and hapless housemate Jack, into their attic to turn off the water supply.

But when Ben - Alexa's date from the night before - walks in, the door slams, the handle breaks and all four of them are trapped.

Cue The Worst morning-after-the-night before.

As the hours tick by, Ellen nurses her sore head and watches as her best friend falls for this handsome stranger.

Only for a horrifying realisation to hit.

She is sure she knows Ben from somewhere.

Frantically searching her memories, Ellen tries to piece together exactly how they've met before.

When a distant memory finally comes to her, she desperately wonders: could Ben really be who she thinks he is . . .

And more importantly, what on earth is she going to do about it .