<Li> Steven Robertson as Sandy Wilson, detective constable (Series 1--) </Li> <Li> Lewis Howden as Billy McCabe, police sergeant (Series 1, 3--) </Li> <Li> Erin Armstrong as Cassie Perez, Jimmy's stepdaughter (Series 1--) </Li> <Li> Mark Bonnar as Duncan Hunter, Cassie's biological father (Series 1--) </Li>

What is relationship between perez and hunter in shetland