The police thriller from the makers of Line Of Duty was previously confirmed to return after the first episode pulled in more than 13 million viewers.
They all proved to be big hits with audiences over the last year.
She's currently playing DCI Amy Silva in Vigil, which is made by the same producers as the BBC hit cop show.
Set designers were not allowed blueprints for real submarines to create the setting for the thrilling new series – this is how they managed it.
Just when it looked like DCI Amy Silva had found Craig Burke's killer, there was a major curveball.
There was a surprise in store for viewers just eight minutes into Sunday night’s first episode.