More gasping follows when Daniel Sullivan's production stages the scene Shakespeare forgot to write: the forcible baptism of Shylock by burly Christians.
Al is a magnificent Shylock -- watchful, haggard, feisty and unhappy -- and the fifth act in Belmont takes on a whole new meaning of resentment at his treatment: his daughter Jessica, who's eloped with Lorenzo, is less than amused by what Portia and Nerissa have done: turned the tables and condemned her father.
We suddenly see that the play is about trials and tests on every level. Bassanio has failed his by giving away his ring to his own disguised partner. Ditto, Gratiano to his.
Lily Rabe, who unwittingly caused a delay to the opening in the tragic circumstances of her mother Jill Clayburgh's death, comes through triumphantly as Portia.
I had prepared for the Sunday matinee by visiting my old friend, playwright Michael Weller, in Brooklyn. Weller saw The Merchant in Central Park in the summer and reckons that the Belmont scenes make sense for the first time in his experience.
He's finishing off a new play and is about to go to Australia for the world premiere of his Dr Zhivago musical, which he's written with Lucy Simon, Carly's sister (she wrote The Secret Garden).
It was glorious down there by the bridge, and the hot new performing space, St Ann's Warehouse, currently home to Kneehigh's The Red Shoes.
We all had brunch in Bubby's -- I enjoyed my first ever apple and bacon omelette -- which kept me going through Al's performance, a meeting with a New York editor friend, and the glorious blast of American Idiot at the St James's.
I'm the only person in the world who's never even heard of Green Day, but I liked their Clash-style music (with melodic tender bits, too) very much indeed. American Idiot's directed by Michael Mayer as a nostalgic synthesis of Hair, Rent and Spring Awakening.
But as I head back to London for The Rivals on Tuesday night at the Haymarket, I shall be haunted by Al chasing me down a Venetian back alley demanding justice, and revenge, and his ducats, and his daughter.
The Michael Radford film in which he appeared (with Jeremy Irons as Antonio) was pretty good. But this is better. And I think the majority of his fellow actors could give a lesson in Shakespearean verse speaking to the current RSC.
They have all been encouraged to make the poetry stand up and reveal its meaning through exhalation. It's a rare treat to sit in a theatre where the audience is literally hanging on every word. And, in Al's case, every damned look.