Sometimes when stories open up as they have to after their initial stages we veer off the main path into unnecessary side alleys but the impressive aspect of this story is that each of the plot strands is intricately connected to the others even if we don’t exactly know how. The mysterious Boreal makes a welcome return to the centre of things this week and remains an impressive presence in a series packed with them. His casual menace is matched by deeds this time as he uses his brief acquaintance with Lyra to steal the altheiometer. The way it is done is a bit clumsy but nonetheless sets up an impressive scene at the end of the episode. Arlyon Bakare is one of those actors who can make a point with economy and the character’s controlled ambition is a highlight in a week that ups the game for all concerned.