Law & Order: UK S07E06 - Dependant

A gay father is found beaten to death and his adopted son is missing. Ronnie and Sam track down the baby's biological parents, a recovering drug addict and her former boyfriend, who are taken into custody. But their stories don't match up so who is guilty of murder and why? Meanwhile, there's tension at the CPS when Kate struggles to view the case objectively and puts the outcome in jeopardy.