Stephen and Dan head to Sacramento to interview Detective Amy Crosby, who led the US cold case investigation of Chris and Peta’s murders. We hear the extraordinary timing of her investigation starting at almost the same time Chris’s sister, Penny Farmer, gets Greater Manchester Police to reopen the case.

The evidence stacked against Boston looks compelling but when Stephen and Dan meet prosecutor Matt Segal they find him less than upbeat about how likely a conviction would have been in this case. Surprised by his gloomy assessment they speak to Boston’s public defender, Lexi Negin. It’s the first time anyone’s heard what Boston’s defence was going to be – and what Lexi reveals turns everything on its head.

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