There is a particular quality to a theatre that has been full every night for a fortnight. The Bellvue smells of it — old velvet warming under 380 bodies, the faint waxy residue of the Act II lamplighting sequence, and something less identifiable that may simply be the scent of a building that has remembered what it is for.

The Lamplighter’s Oath completed its fourteenth evening performance on Tuesday. It has not had an empty seat since opening night on 10 April. Norah Fell, who has processed 4,200 tickets from the box office — by hand, in a ledger, because the Bellvue has never owned a mechanical till — reports that eight performances remain before the Thurston Brothers arrive on 2 May to begin the fly tower repairs. The final performance is 30 April.

Thomas Ashworth’s Edmund Vale has undergone the transformation that only sustained performance produces. The schoolteacher who arrives at the stage door at 4 PM each afternoon — jacket over his arm, lesson plans in his briefcase — becomes, by the time the house lights dim, something larger. His Act III council address, in which Vale demands that the city extend gas lighting to the working-class districts, silences the house every night. On Saturday, a man in the upper gallery wept.

Nessa Holloway’s Clara — Vale’s daughter, who inherits his stubbornness and channels it into something fiercer — has become the production’s quiet revelation. Where Ashworth commands, Holloway unsettles. Her Act IV confrontation with the council chair has acquired a stillness that opening night did not have. After Tuesday’s performance, three people waited at the stage door to speak to her. She spoke to each of them, and then walked home alone along Marchmont Street.

The letter from Ruben Glass arrived on Friday. Glass, who attended opening night in a reserved front-row seat and left through the side door without speaking to anyone, had not been heard from since. The letter was handwritten, addressed to “Augustin Fell, Director, The Bellvue Theatre, Marchmont Street,” and arrived by ordinary post from Caldwell.

It read, in part: “I have been in the theatre forty years and I have learned to recognise the moment when a production stops being a production and becomes the thing itself. You have reached that moment. The fly tower will hold. The play will last longer.”

Fell pinned the letter to the lobby wall beside the 1983 programme that an anonymous donor had enclosed with a fifty-florin cheque during the fundraising campaign. He stood looking at both for some time. Then he went backstage to give notes.

Felix Wainwright’s lighting, which was praised on opening night, has if anything improved. The Act II lamplighting sequence — in which Vale, played by Ashworth, lights the stage lamps one by one with a real taper — remains the production’s defining image. Each flame catches differently. The audience holds its breath each time, as though the outcome were in doubt.

Line seven held on Tuesday. Ruth Kirby, who has managed the Bellvue’s temperamental fly tower for fifteen years, allowed herself what witnesses described as a small nod.

The box office has begun processing refunds for tickets sold for dates after 30 April, when the theatre closes for repairs. Fell estimates the Thurston Brothers will require six to eight weeks. The Bellvue will reopen, he says, in late June or early July. He has already chosen the next production, though he will not say what it is.

“I have notes,” Fell said, which is what he always says.

Constance Fell’s seat — second row, far left, held for the aunt who ran the Bellvue from 1971 until her death in 2006 — still holds an unopened programme each evening. No one has sat in it.