Daniel is running the Chilean desert.
Ayelen is speeding across it in the opposite direction.
When the earthquake hits, they become reluctant travelling companions, in a desperate bid to find out if Ayelen's family have survived.
An adventurer and a rebel meet head on.
Daniel is a young free runner, who has been all over the world, jumping across cities everywhere but never really seeing them.
His latest goal is to run solo across the Atacama desert in Northern Chile, a new extreme challenge.
He's earning a huge amount of money by being filmed at the end of his run drinking a particular extreme sports drink.
But he has to get there on a certain day, and his time is tight.
Ayelen 30 something year old Chilean woman, who has lived in the Uk for most of her life.
She has come home on a family reunion with her mother but has run out after yet another family row.
She has 'borrowed' a run down 4 by 4 from the garage where her brother works - and she is travelling across the desert alone.
Then all of the sudden the earthquake hits.
Ayelen's car is thrown off course, she is trapped and Daniel, who has seen it all from a nearby ridge, is forced to rescue her.
He is reluctant to break his meticulously planned run - but you can't abandon a human being in a place like this.
Their subsequent journey across the desert is a life changing experience for both of them.
Terremoto is written by Catrin Clarke, an experienced television and radio writer, and based on her own knowledge of Chile and running the desert.
Guy Marchant.Richard Harrington
Chilean driver...Ernesto Cantu
Acoustic guitar and folksong performed by Héctor Daniel Saez Cárdenas
Director Polly Thomas for BBC Cymru/Wales.
As Daniel runs and Ayelen drives across the Chilean desert, an earthquake strikes.