Missing at Christmas: How family of missing Billy Davies cope
Not knowing where a loved one has gone is agonising on any day.
But perhaps no time is more difficult than Christmas for the families of missing people.
Billy Davies, from Mountain Ash, Rhondda Cynon Taff, went missing on 18 February, 1997, when he was just 16, and his family still do not know what happened to him.
His niece, Anna Davies, said: "It's that one dinner missing, you know you're never going to get that back."