The farm is in lockdown and police search teams swarm over the property, as the Bains are rocked by Azir's revelation. Believing the identity of the killer lies in the reason why Ellen left Shetland, Tosh and Calder arrest Bobby Bain. An explosive interrogation does nothing to dampen Calder's suspicions.Back at the farm, physical evidence of Ellen turns the spotlight on another member of her family, as the police continue to piece together her final movements.As the Bains begin to unravel, Grace remains defiant, but her silence only serves to confirm the existence of a secret at the heart of this family. Piecing together all that they have learnt so far, Tosh and Calder move ever closer to an answer beyond what either of them could have imagined.