Melodramatical moments like the Macavity reveal should look a bit silly when everyone's just in rehearsal gear, but... not if everyone commits like this.
Thomas Inge as Macavity is just living his best life (and somehow looking even more indecent in that loose top than in all the many shirtless thirst traps he posts on insta, but I digress).
Demeter (Ella Nonini) rushes past carrying the Deuteronomy coat, followed by Cassandra (Natalie Bennyworth, white top), and possibly Bombalurina (Suzie Melloy, black top, far left in the first few frames) who is backing away in horror as she realises.
On the far right we see Skimbleshanks (Hayden Baum, black top and green headband) shifting from 'concerned reach??' to 'PROTECTOR STANCE AND SNARL'—and what prompts that change? It's Macavity lashing out at Mungojerrie (George Hankers, green shirt with his back to us). Jerrie feels the blow (physical or magical) and flinches away, half trying to cover his eyes and half turning toward Rumpelteazer (Dominique Hamilton, pink singlet and red ponytail, bottom left corner).
The black shirt and back of a red curly head in the first few frames are Munkustrap (Rafe Watts), who reacts before Macavity lashes out at Mungojerrie: he was tense already, and it's the sight of Macavity's face that he reacts to. He's already realising things have gone very wrong...
... and so is the other Munkustrap (Benjamin Colley, swing and first cover Tugger/Munk), sitting down at the edge of the stage. Ben's focus is locked on Rafe—and he even half snarls along with him!
(Thalia Burt, on the other hand, is busy being resident director, not actor.)
(The three other booth swings are at the table behind her: left to right, Andrew Dunne, Holly Willock, Caitlin New.)