Imagine you can see enemy moving (for example) between yours 4. and 5. move.
Knowing that move order is alway ABBAABBAA...,
the only* possibility is, that it's your opponent 1st move turn:
op, you(1), you(2), op, op, you(3), you(4), op(visible), you(5)
as the opposite situation is not possible:
you(1), op, op, you(2), you(3), op, op, you(4) [op. move can't be executed here]
Ofc. you can use it only, when opponent's move is shown before your last move.
* assuming no OP card involved
Edited 2/16/2016 12:30:44