Maguire and his colleagues are stumped as to how a gang of thieves are breaking into places, and leaving no trace as to how they're breaking in. The urgency to convict the gang is increased when a night Watchman is killed.
There are definitely some interesting ideas here, but ultimately Picture Puzzle is a somewhat forgettable episode.
There are a few holes in the plot I think it's fair to say, I could quite work out that opening sequence, and there is one really annoying scene, where Maguire shouts to his colleague 'there he is' about an armed man standing no more than two foot away.
Michael Balfour, who played the ill fated Allen, I could have sworn he appeared in the previous episode, I may be wrong.
I'm not sure anything about this one will stick in the mind.
6/10.