Given that the BBC press people handed out a list of spoilers the length of a sea league, writing about submarine-set drama Vigil was always going to be easier once its opening two episodes had aired. That said, it would still be unfair to reveal too much for those who might be looking at a future binge of the broadcaster's latest attempt at thrilling a Sunday night audience with a host of cliffhangers, twists and misdirections.

So, without giving too much away, Suranne Jones plays Amy Silva, a detective chief inspector with a troubled past (tick) whose previous trauma has left her with a fear of confined spaces, specifically relating to being underwater. All too inevitably then, she is whisked away by helicopter and dropped slowly into the HMS Vigil, a nuclear sub whose activities are being tracked by an unidentified enemy vessel which has already laid waste to a small trawler and its hardy crew.

National security issues are not Amy's concern as she's been handed the task of investigating the shock death of a seemingly erratic crew member in their cabin. It would be fair to say that none of the navy folks are particularly delighted to have Amy on board, a mix of irritation at a snoop getting in the way of their procedures and protocols, and probably a fear that some uncomfortable truths will be sniffed out. Among those blocking her route to an easy life are a wily semi-hostile commander Newsome (Paterson Joseph) and a slimy full-on hostile Prentice (Adam James) who is second in charge. Meanwhile on dry land, Amy's partner in (solving) crime and also in love is Kirsten Longacre (Rose Leslie) who is doing her bit on the case without risking claustrophobia or damp socks, and which involves the most unlikely discovery of a vital clue in the history of small-screen sleuthing.

Asides from that preposterous moment, dodgy dialogue and ridiculous plot devices (two other BBC Sunday-night drama tropes) are mercifully sidestepped here for enjoyable performances and actors being allowed to talk in their own regional dialects (notably Martin Compston and Rose Leslie). Suranne Jones is once again very believable in the leading role though it can be a challenge watching her in a cop show after A Touch Of Cloth, Charlie Brooker's Airplane-style spoof. Vigil could turn out to be the crime thriller of the year or another one of those shows which leave viewers perplexed and annoyed at its conclusion. In four episodes' time, we'll all know the truth.

Vigil, BBC One, Sundays, 9pm; episodes 1 & 2 available on BBC iPlayer.