This is one of those memorable episodes where it's part tragic, partly a thriller lot of action
Alex Walkinshaw is somewhat a good actor, yet so is Todd Carty, and I prefer Gabriel over useless Smithers.
I don't see Sergeant Smithers the important bigshot of this program or this episode, he plays a genuine grieving crybaby after girlfriend is killed, he furiously storms into Superintendent Adam Okaro's office: accusing him of delaying the ambulance, attacking David Radford (from personal assumption he murdered Kerry after made a threat to kill her), and then sitting very depressed and alone, and Gina acting like his mommy dearest, keeps defending him whenever he's misbehaving badly, blaming other people, even her (saying Kerry needed 24 protection, not suspension) and Gina won't accept his warrant card? Also, I wonder what discipline Smithers receives after Irene Radford made complaint to Gina about Smithy attacking David, his aggressive behaviour and planning to take law in his own hands (unsurprisingly, it's what they usually do). Kinda strange Rob Thatcher seemingly defending the Radfords.
DI Morell from MIT (Murder Investigation) returns played by Tanya Franks mainly known as Tanya's sister Max Branning's ex-wife Rainie in EastEnders. She gets an investigation into Kerry's life and who could've killed her, even interviewing those who left messages on her phone including June and Andrea (who Kerry could've exposed her reputation of undercover journalist).
As for main antagonist, this is one of the best episodes with evil PC "Gabriel" Kent who just shot Kerry, and as he quickly bags the rifle etc he accidentally knocks some bullet casing (guess as he left his fingerprints on it) down a drainpipe at a disused building and can't get through some large gate to retrieve it, so he had to leave the incriminating evidence behind - sort of see the classic worry and heart-pounding desperation in him. At least, he calmly volunteers to revisit the crime scene with Andrea and Ken Drummond, and seemingly wiping the bullet casing clean. Ken and Suzie Sim both later say the casing is clean of fingerprints and gunman is clever using using disguise (like a copper or construction worker, or utility engineer) without causing suspicion.
Gabriel thinks he has covered his tracks barely, despite some suspicions from June Ackland (who told Kerry about his false identity) and Steve Hunter - when some elderly man made complaint Gabriel nearly run, by police car, over near the crime scene, then Gabriel somewhat manipulated the old man with incorrect registration plate on police car and joyriders. The elderly man was definitely crossing the road from between parked vehicles - that's considerably dangerous. Just as Gabriel thought got he got away with killing Kerry who could've exposed his true identity posing as his adopted brother, Morell brings up some surprise revelation to him about Kerry: she was few months pregnant from him, which resulted when Gabriel viciously raped Kerry. Oh, dang!