A £10,000 reward is being offered by detectives investigating the suspected murder of a missing father and son who disappeared in Spain five years ago.
Daniel Poole and his son Liam were last seen travelling in Malaga, southern Spain, in 2019.
Since 2022, Sussex Police have been treating the case as a murder investigation and on Monday announced they were offering a reward for information that led to an arrest and charge.
Detective Chief Inspector Simon Dunn said the force believed people in the UK "may hold vital information" about the case.
It comes after Liam's grandmother Kathy Catney told the BBC in 2019 she feared the pair had travelled to the country for a possible drug deal, and had been killed.
DCI Dunn told Sky News he was working on the basis "they travelled to Spain to see friends for a holiday" and was keen to "understand the details behind the disappearance and what I believe [was] the murder of Danny and Liam".
The father and son, from Burgess Hill, West Sussex, then aged 46 and 22, hired a grey Peugeot 308 with the registration plate 0254 KTM when they arrived in Spain on 31 March 2019.
However, the car was later found abandoned by Spanish police despite their luggage and passports being left at the hotel.
'I pray that someone could give our family closure'
Sussex Police are taking legal steps to take over the investigation from Spanish police.
Lauryn Poole, Danny's daughter and Liam's sister, said: "Not a day goes by that I don't wonder what life would be like with my dad and brother in it.
"Every day that goes by sees a thought pop into my head about what truly happened and what their last moments might have been like - these thoughts often keep me awake at night.
"I beg and pray that someone could give me and our family the closure we need to move on from the sleepless nights and that I can give an explanation to my dad and brother's growing family one day."
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'I do think Liam's died, I think he's been killed'
Ms Catney travelled to the Spanish golf resort in 2019 where they had stayed to try to track down her relatives.
She said the pair did not play golf and that a barman had told her they were "wrong'uns" when she asked after them, the BBC reported.
"I do think Liam's died, I think he's been killed. I hope he's not at the bottom of the sea," she told the broadcaster.
'We always suspected he was up to no good'
Ms Catney added: "I knew he [Daniel] had done time for drugs because he was with my daughter that time, we always suspected he was up to no good but again we just didn't ask questions.
"I knew he was going to Spain to meet up with somebody to do some sort of deal. Whether that was property [or] drugs I really didn't know."
She also claimed the family received an anonymous demand for a £100,000 ransom and raised the money but heard nothing further.
DCI Dunn told Sky News the family were "desperate for answers".
"They've endured this nightmare for the past five years. And they are absolutely desperate for... anybody that can assist with understanding the circumstances of their loved ones disappearance," he added.
(c) Sky News 2024: Police in Sussex offer £10,000 reward for information linked to father and so