There is a reliable predictor, a player, and two boxes designated A and B. The player is given a choice between taking only box B or taking both boxes A and B. The player knows the following:[4]

Box A is transparent and always contains a visible $1,000.

Box B is opaque, and its content has already been set by the predictor:

If the predictor has predicted that the player will take both boxes A and B, then box B contains nothing.

If the predictor has predicted that the player will take only box B, then box B contains $1,000,000.

The player does not know what the predictor predicted or what box B contains while making the choice.

(explaination from https://en.m.wikipedia.org/wiki/Newcomb%27s_paradox)