Wedi’i dympio gan ei chariad, mae Ally yn ddigartref, yn ddi-gyfeillgar ac yn ddi-waith… ond o leiaf mae ganddi Malcolm, cath ei hen partner.

Ar ôl taith hir ar y trên, mae’n cyrraedd cartref ei thad yn Sheffield, yn barod i blygu ei hun yn ei duvet ac aros ar y soffa hyd y gellir rhagweld. Mae gan ei thad syniadau eraill. Galwad ffôn yn ddiweddarach, ac mae Ally yn cael ei haduno gyda’i barf (beard) gyntaf erioed a’i hen ffrind, Jeremy. Mae yntau hefyd wedi torri ei galon ac yn byw gartref eto. Felly, mewn ymdrech i ddal ei gilydd i fyny, mae’r pâr yn penderfynu cofrestru ar gyfer yr hanner marathon lleol.

Brutally dumped by her girlfriend, Ally is homeless, friendless and jobless… but at least she has Malcolm. Wounded and betrayed, Ally has made off with the one thing she thinks might soothe the pain: Emily’s cat.

After a long train journey she arrives home to her dad in Sheffield, ready to fold herself up in her duvet and remain on the sofa for the foreseeable. Her dad has other ideas. A phone call later, and Ally is reunited with her first ever beard and friend of old, Jeremy. He too is broken-hearted and living at home again.

In an inspired effort to hold each other up, the pair decide to sign up for the local half marathon in a bid to impress their exes with their commitment and athleticism.

Given neither of them can run, they enlist the support of athletic, not to mention beautiful, Jo. But will she have them running for the hills… or will their ridiculous plan pay off…?