This is about the 1987 film Moonstruck (Academy Awards for Cher and Dukakis), about Loretta Castorini who is engaged with Mr. Johnny Cammareri but then falls in love with his estranged brother Ronny Cammareri.
Mr. Johnny is away in Sicily, because his mother was breathing her last breath. In the meantime, his fiancée was supposed to organize their wedding. She falls in love with Ronny and Mr. Johnny returns unexpectedly early. The climatic scene at the end
From the script:
MR. JOHNNY Well. I told my mother that we were to be married. And she got well. Right away. RONNY I'm sure she did. MR. JOHNNY It was a miracle! LORETTA Johnny, I have something to tell you. MR. JOHNNY I have something to tell you. But I must talk to you alone. LORETTA I have no secrets from my family. MR. JOHNNY Loretta, I can't marry you. LORETTA WHAT? MR. JOHNNY If I marry you my mother will die. The Old Man laughs a loud sudden laugh, and then subsides. LORETTA What the hell are you talking about? We're engaged. RONNY Loretta, what are you talking about? LORETTA I'm talking about a promise. You proposed to me! MR. JOHNNY Because my mother was dying! But now she's not.
For sure, this is an unexpected turn of events, since the viewer saw Loretta's and Ronny's love blossom, so what would happen when Mr. Johnny finds out? But then, Mr. Johnny himself breaks off the engagement. Wikipedia says
When Johnny finally arrives, he breaks off the engagement, superstitiously believing that their marriage would cause his mother's death.
Even if it's just superstition, what is the root of such a belief - after all, breaking off an exgagement is quite a big step to take and the announcement just brought her back to life, so to speak (sounds good, doesn't it?). Is his mother somehow involved (Ronny's remark (see script): "You're forty-two years old, Johnny, and Mama is still running your life."), but if so, why? The old man's reaction (laughter) is also interesting.
Why does Mr. Johnny believe that his marriage would kill his mother?