Stephen and Dan head to Savannah, Georgia to meet Vince Boston – son of suspect Silas Duane Boston. Vince (then 13) and his younger brother, Russell (12), were on board the ‘Justin B’ with their dad, when they met Chris and Peta in June 1978. Through Vince’s words and Peta’s letters we hear about their happy first few days as they sail south from Belize. But as Peta’s writings grow more troubled, Vince details how his father’s temperament grew more and more menacing. Vince’s account turns into a horror story as he recounts how he was made to stand guard over Peta the night before she and Chris were killed. Vince tells Stephen every detail of the unfolding plot that leads to their drowning. The question is – what had his father done to him to render him so silent in the face of such terror?

Find out more about the case here: www.bbc.co.uk/paradise