Wilson, Xavier, Yoeman and Zenger were playing a card game, in which three cards, from each player's holding, remained to be played; and in which one of the four suits - clubs, diamonds, hearts, and spades (denoted respectively as C, D, H and S)- was the high suit. A high suit is just like a trump suit in many card games.
The play of four cards, one from each player's holding was a
trick, and the suit of the card played first in a trick was the
suit led.
[1] The distribution of the four suits on the cards held by the four players was as follows:
Wilson's holding -- C H D
Xavier's holding -- C S S
Yoeman's holding -- C H H
Zenger's holding -- S D D
[2a] A player had to play a card in the suit led, if possible, at each trick.
[2b] If [2a] is not possible, he had to play a high suit.
[2c] If [2b] is also not possible, then he could play any card.
[3] Each of the remaining three tricks contained in part: the suit card led, just one other card in the same suit as led, and a high suit card which won the trick.
[4] A player who won a trick had to lead at the next trick.
Which suit was the high suit?
There are three cards in each suit, and a high card in each of the tricks, so a high card is never led (because every trick has at least exactly two cards in the suit led). Each of the other suits is necessarily lead once.
Assume C is the High suit. Then the suit led must be a heart (otherwise two people trump the 1st trick). But X wins and must lead an S, so two people trump the 2nd trick. Therefore, C is not the High suit.
Since the high suit is S or H or D, and since a trump is never lead, then one player won the first trick, exited by leading a non-high-suit, and won the last trick.
Assume the high suit is S. Then X wins the first trick and leads a C. The suit led at first must be a D, because Z does not trump. Then Z must win the 2nd trick, but this does not work because this has Z leading a D at trick 3. So the high suit is not S.
Assume the high suit is H. If an C is lead initially then nobody trumps, and if an S is led then two people trump, so a D is lead initially. But then a C is led at trick 2, and nobody trumps. So the high Suit is not H.
Therefore, the high suit is D. Z trumps the first trick (it must be a heart lead to avoid 3 clubs on a trick), leads an S which is trumped by W, and then W leads a club which is trumped by Z. This works if X discards a C on trick 1 or Y discards a club on trick 2, but not both.
Trumps rule (spoiler)
