[chriswarbo]

Bell's inequality refutes theories with local hidden variables (e.g. some unknown property of particles or spacetime). That leaves two possibilities: no hidden variables (the results truly are non-deterministic) or non-local hidden variables (e.g. some property which exists outside the spacetime which we're constrained to)

[devishard]

There's a third possibility, superdeterminism, in which literally everything is determined by previous conditions, so that no communication is needed, even via a property outside of our spacetime, because everything was determined by preconditions.

Think of it this way: you set two clocks to the same time. The next day, they both have the same time on them. This isn't because the clocks are communicating via nonlocal hidden variables, it's because their precondition was the same and the sequence of events which followed was deterministic.