Perhaps the music isn't the most memorable but it's economy and very understated telling of this tale is very effective, benefitted by fine performances all round.
The music of the first act (part one effectively)is easy to follow because, like Janacek, Weir's music follows speech patterns quite closely. The revelation that the husband's friend knows the name of his wife's dog from childhood brings some quite matter of fact story telling to a chilling close.
The second act (part two) follows the descent of both husband and wife into madness and death as the now murdered friend appears in a series of guises taking them back to their to their troubled childhoods. This is part ghost story and or moral tale but however you look at it it is very effective and Judith Weir's music serves this strong and disturbing tale. I'll not say any more to spoil the tale; suffice to say it is well worth the journey. Highly recommended.