"Blood Knot" is an early play by South Africa's Athol Fugard.
There are only two characters in the play, a pair of brothers named Morris and Zachariah. Both were raised by the same black mother, but had different fathers, and Morris is much more fair-skinned than Zachariah. Morris can pass for white, and has done so in the past, but now he has returned to live with Zachariah in a small, miserable shack in the "colored" section of Port Elizabeth. Morris keeps the house, while Zachariah works to support them both. They're saving money in hopes of buying a farm of their own some day. Both Morris and Zachariah have rich imaginations, and have taken part in role-playing games together since they were small boys.
The lonely Zachariah has struck up a pen-pal relationship with a white girl, and entertains fantasies that she might fall in love with him. The more level-headed Morris tries to disabuse Zachariah of such notions, and warns him that in segregated South Africa, such a relationship can only mean trouble, especially since the girl has indicated in letters that she has a brother who's a policeman.
Morris' fears are soon realized, as Zachariah's pen-pal writes to say that she's coming to visit Port Elizabeth, and wants to meet Zachariah. Zachariah must face the tragic truth that he can never have a future with her, that she can never love him, and that she would be horrified to see who he really is. To avoid having her meet Zachariah, the brothers agree to have the white-looking Morris meet her, and pass himself off as Zachariah.
To prepare for the date, Morris buys some fine "white" clothes with the money that he and his brother had been saving. When he puts on the clothes, he begins to adopt the white mannerisms and speech patterns that he'd learned years earlier, when trying to "pass" in white society. As he does so, he begins to treat his brother like an inferior, as any middle-class white South African would treat a black servant.
When a letter arrives, indicating that the girl will not be coming for a visit after all, Zachariah and his relieved brother Morris begin a new role-playing game. This time, the game take bizarre twists. It becomes evident that Morris secretly holds his brother in disdain, and Zachariah secretly harbors thoughts of killing Morris.
The play ends with no real resolution. Morris and Zachariah will, apparently, remain together for many unhappy years to come, needing each other, but unable to bridge the gap brought about by their respective skin tones.
"Blood Knot" debuted on Broadway in 1964, with J.D. Cannon as Morris and James Earl Jones as Zachariah.