The story is based on the Middle English romance Sir Gawain and the Green Knight.

[4] The plot of Gawain is ideally suited to Birtwistle's approach to musical structure.

The synopsis also indicates many points where recurring motifs are heard: trios of door knocks; the return to the Arthurian court at the end of the opera with the same mood of boredom seen at the beginning; the members of the court gradually recovering from Gawain the items they gave him at the end of act 1.

There are many occasions when one character will simply repeat one line of text always set it to the same melodic phrase, but this is not the same as using a leitmotif.

The conductor Elgar Howarth has arranged the orchestral suite Gawain's Journey from music in the opera.

Also present, but invisible to the rest, are Morgan Le Fay and Lady de Hautdesert, who are conspiring to bring down Arthur.

Instead, the fool posits a series of identity riddles, while Morgan Le Fay promises him entertainment soon enough.

The Knight reiterates on its terms, and declares that he has come in search of a hero, someone brave enough to take up his challenge.

The still unseen Morgan Le Fay and Lady de Hautdesert sing of their plan, focused on provoking Arthur's vanity.

Gawain must travel to the north, to the Green Chapel, the instructions echoing as the Knight rides out of the court.

Through it all, Morgan Le Fay continues to chant her one line: 'Now with a single step, your journey starts'.

They await Gawain's arrival, singing lines of text drawn from Morgan Le Fay's taunting.

When he states that his wife will keep Gawain company while he himself is out hunting, Bertilak is struck with jealousy and suspicion.

The following day, while her husband is out hunting, Lady de Hautdesert comes to Gawain's private chamber.

This puts Gawain in a dilemma, with the conflict between obeying the commands of a lady and not committing adultery.

The Green Knight calls Gawain's name from offstage, exactly as he did when he left Camelot a year earlier.

Morgan Le Fay removes the enchantment that disguised Bertilak as the Green Knight.

Two knocks at the door initially reveal no one present, until the third time, when Gawain enters, his identity obscured by his great coat and the snow.

As the court settles down, consoling themselves that 'all is as it was, with nothing changed', they help Gawain remove the garments they gave him at the end of Act 1 for his journey.

This alienates the court, and the opera closes with Morgan Le Fay singing of the discord she has sown.

The emphasis here is on the flawed hero, revealed to be fearful for his own life and willing to lie and deceive in order to keep it.