'Something clicked and I just decided to leave'
Police received 864 calls a day regarding a missing or absent person in 2014-15, according to Police Scotland and 41 police forces in England and Wales.
Most those who disappear will return home quickly, normally within a week, But a small proportion - around 1% - are still not found a year later.
So what makes someone walk out of their own life?
Joanna Gosling spoke to Shelley MacKenney, who went missing when she was 22 for 18 months, Professor Hester Parr who is running a research project looking at why people leave and Colin Sutton, a former senior investigating officer for the Met Police who has worked on many missing persons investigations.
Duration:
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