The father of missing Milton Keynes teenager Leah Croucher says he knows "a certain person" is keeping information about his daughter from the police - and will name him if he does not come forward.
Speaking a year on from her disappearance, Leah's family said they completely broken and were struggling to cope with still not knowing what happened to her.
The teenager was last seen at home in Emerson Valley by her family at 10pm on Valentine's Day 2019 and the last known sighting of her was the following day, February 15, at Buzzacott Lane in Furzton. She was 19 at the time.
Police have issued a fresh appeal for information on the one-year anniversary.
But Leah's father John Croucher believes he knows someone who has vital information about his daughter - and has issued them an ultimatum.
Mr Croucher along with Leah's mother Claire and her sister Jade have given interviews about what life has been like over the last 12 months.
They all agree the trauma has destroyed their family.
The search for Leah has seen officers visit more than 4,000 homes in Milton Keynes. Specialist teams, drones and helicopters were also deployed.
Police say her phone and bank account have not been used since she disappeared.
Witnesses had previously come forward saying they had seen someone of Leah’s description “angry, upset and crying” by a lake on the day she disappeared. The witnesses were walking by Furzton Lake at the time, close to where Leah was last seen.
Specialist officers searched the lake in October but found nothing.
Leah’s parents say they think their daughter was taken and have questioned why she would "just disappear".
And while police have yet to find evidence of a third party being involved, they admit they are unable to rule out the idea that Leah came to harm after she "effectively vanished into thin air".
Nine month's after Leah was last seen, her brother Haydon took his own life - unable to cope with not knowing what happened to his sister.
He family said they hold whoever took Leah responsible for his death too.