Nick Berry and Stephen Tompkinson return for the concluding series of BBC crime drama. 'In Deep'. It's been a testing time for Liam Ketman (Berry) and Garth O'Hanlon (Tompkinson). Once the stable partner in the relationship. Liam has become a walking time bomb since the brutal murder of his wife, and only Garth's constant vigilance can keep him from stepping over the edge. Garth, meanwhile, continues to lead a shadowy double life, giving few details away and ruthlessly pursuing the job in hand. With only each other to trust, the stakes are higher - and deeper - than ever before.