But I don't know what happens tomorrow.

[shootingstar]

(Mrs Elm, the librarian, speaking)
'it's hard to predict, isn't it?' she asked, looking blankly in front of her as she moved a black bishop across the board to take a white pawn. 'The things that make us happy.'
. . .
'Yes,' said Nora. 'It is. But what happens to her? To me? How does she end up?'
'How do I know? I only know today. I know a lot about today. But I don't know what happens tomorrow.'
(The Midnight Library by Matt Haig, episode The Chessboard)

I don't understand why the author doesn't use the future in the second part of the denoted sentence. My suggestion: "But I don't know what'll happen tomorrow". Is there any grammatical reason not to do so? What does it depend on?

 

[5jj]

One possibility: the speaker sees every day as 'planned' in some way. They can see the past and present, but cannot see the future. They are not privy to the plan.

 

[Skrej]

Consider the similar usage of the present tense for future occurrences when referring to planned or scheduled events.

My flight leaves at 1:30 p.m tomorrow.
The concert starts at seven.
I have a dental appointment on the 23rd.

 

[jutfrank]

I think the idea here is likely that the future is already written, like a book that the speaker doesn't have access to.