Take out Nicola Walker and Stephen Mangan and you have nothing more than basic , cheesy soap . However it's dressed up as serious, sophisticated drama which would not fool a five year old . The leads are excellent but are badly let down by the rest , especially the other two sisters who seem to be either reading off cue cards or simply trying to make up the plot as they go along . The once interesting weekly cases have now been set aside for ever more ludicrous ' twists ' that can be spotted a mile away . It's a pity because this could have been a really good series but has been badly mishandled.