Beneath the New Year's Eve fireworks, shy science-nerd Mel and slacker songwriter Sid get pregnant on their first date. Any sixteen-year-olds would expect trouble – but this is Northern Ireland 2018, where abortion is still illegal. Mel's religious parents insist she must keep the baby, whilst Sid's feminist mum pushes for a termination.
Mel and Sid are determined to do this together, but they soon discover that pregnancy is totally different for boys and girls. When their relationship starts to fall apart under all the pressure, Mel finds herself feeling alone with the impossible dilemma of the Little Bang growing inside her.