Out of This World

Someone who has never held a deck calls red or black for card after card, face down, and gets every one right. Paul Curry published it in 1942 and magicians have been calling it the best card trick ever made for eighty years.

Curry died in 1986. The trick has been in print, on Wikipedia and on video for decades, and there is no secret left to protect — but there is something almost every explanation gets wrong, or quietly skips, and it is the most interesting part.

Call them yourself

Twenty cards, face down. One line is labelled red and the other black — a single marker each, to begin with. Call each card exactly as a spectator would. You will not see a face until the end.

Why it works

Because while the deck is feeding cards of one color, both lines are equally right. The spectator is making a free choice that cannot be wrong, because every card available to them at that moment is the same color.

The deck is separated — reds together, blacks together. For the first half, every card coming off it is red, so it does not matter which line receives it. Halfway through, you change the markers over. Now the second half arrives, all black, into lines whose labels have swapped hands.

The part almost nobody explains

Work it through and you hit something odd. The two markers must be different colors — that is the whole premise. But both lines receive the same color at the same time. So when the first half is red, only the line labeled red can be correct. The other line is quietly collecting reds under a black marker.

One line comes out perfect and the other comes out exactly backwards. Not partly wrong, not randomly wrong — inverted. Right cards, right order, labels the wrong way round.

	First half (all red)	Second half (all black)	Result
Line A	red under RED ✓	black under BLACK ✓	perfect
Line B	red under BLACK ✗	black under RED ✗	exactly inverted

There is no arrangement of two different-colored markers that makes both lines come out right on their own. Every card landing on line A matches; every card landing on line B does not. (Put all of them on one side and the other is empty rather than wrong — which is a curiosity, not a way out.)

And that is the point, because exactly inverted is a gift. A line that is backwards in a completely predictable way can be put right by reversing it — and reversing a line of cards is indistinguishable from gathering one up. So the correction hides inside a movement you were going to make anyway.

Every published handling of this trick resolves the same problem, and they differ only in how. Curry's original, Harry Lorayne's impromptu version, and the handlings sold today all arrive at the same place by different roads: one line is fixed while the spectator is busy with the other.

How to perform it

Separate the deck before you sit down. Reds together, blacks together. That is the only preparation, and the only thing that must not be seen.
Put down two markers. One red face up, one black face up, well apart. These are the labels.
Let them call every card. They choose the line every time, and they cannot be wrong — so let them take as long as they like, change their minds, and talk themselves in and out of it. Every hesitation improves the ending and costs you nothing at all.
Add a second marker to each line at the halfway point. A black one goes on the line that started red, and a red one on the line that started black — so each line now carries two, and the new one is the label from here on. "Let's swap these over, in case you have been favoring one side." Say it casually. This is the only timed moment in the trick: it must happen exactly as the deck crosses from one color into the other, so count your halves before you start.
Let them finish.
Gather the lines — and reverse the second one as you do. Ask them to gather their own line while you gather the other. That is the cover, and it is enough, because they are looking at their hands.
Turn the lines over one group at a time. Four reveals, not one. Spend them.

The one thing that goes wrong

Changing the markers at the wrong moment. Too early or too late and both lines are part-wrong instead of one being cleanly inverted, and no amount of reversing will save it. Know which card you are waiting for.

Making it play

Do not claim it is their intuition. Say you have no idea whether it will work. Then the ending is something you are both discovering.
Never touch a card once they start calling. The strength here is that you visibly do nothing. The marker change is the one exception and it should look like fussiness rather than method.
Let them shuffle nothing. This is the trade for the ending — the deck is set, so keep the handling brief and do not invite an examination you cannot survive. Impromptu versions exist and buy that back at the cost of harder work.

The 21 card trick needs no setup at all, and the Si Stebbins stack is the opposite trade: set the deck once and the arithmetic does everything afterwards.

The method is documented in several places, including Wikipedia, and the published handlings differ from one another — which is itself worth knowing, and is why this page explains the principle rather than one person's sequence of moves.