Borrowed Time

Tilly-Jo could easily pass as nuts according to many in 2015, what with her love for everything retro (especially the music) and love for school. Although she's sad to leave, she finishes sixth form with excellent grades. She gives off the impression that she's happy in 2015, but she knows she doesn't belong there.

After supposedly fainting, she wakes up in an unrecognisable street.
That's because it's in Liverpool, 1959.
And who should come to her aid? No one but John Lennon.