What is the racial identity of the protagonist in "The Wife of His Youth" by Charles W. Chesnutt? What act of heroism does he perform?

In Charles W. Chestnutt's story, the protagonist is Mr. Ryder, whose real name we later learn is Sam Taylor --a black man who is able to pass as white.

We learn early in the story that he belongs to a community of light-skinned black people called the Blue Vein Society. Chestnutt describes it as the following:

The original Blue Veins were a little society of colored persons organized in a certain Northern city shortly after the war. Its purpose was to establish and maintain correct social standards among a people whose social condition presented almost inherited room for improvement.

Though it is not directly stated, that "social condition" is lighter skin, which indicates (phenotypically, anyway) an abundance of European ancestry. White supremacy allowed the Blue Veins to think themselves better than other black people because of their presumed proximity to whiteness. Hence, their assumption that their "social condition" (light skin) "presented almost inherited room for improvement" (i.e., would allow them to form a class above darker-skinned black people).

Entry to the Blue Vein Society required a prospective member to turn over and reveal his or her forearm. If the blue veins were transparent beneath the skin, one would be allowed entry into the group. 

Mr. Ryder is "dean" of this group. Though we are informed that he is not as light as some Blue Veins, "his features were of a refined type, his hair was almost straight; he was always neatly dressed; his manners were irreproachable, and his morals above suspicion." Education distinguishes him, particularly his affinity for English poetry.

Knowing all of this about Mr. Ryder, we are rather surprised when we learn that the unlettered and "very black woman" whom we meet later in the tale is Ryder's wife, Liza Jane, a former slave. She is trying to locate her husband, Sam Taylor. We learn through Liza that Mr. Ryder/Sam Taylor was free-born (like many members of the Blue Vein society), and "merlatter," or "mulatto," a person of biracial identity.

Though Sam was free, he was an indentured servant in Missouri and in danger of being "loaned out" for one thousand dollars. Liza Jane told her husband of the master's plans, which allowed Sam to run away before they could be carried out. Sam does not reveal himself to his wife right away, but takes down her address and says that he will "give the matter some attention."

At the end of this second part of the story, Sam stops at "the mirror of his dressing case" and "[gazes] thoughtfully at the reflection of his own face." We are to understand that he is having an ethical dilemma here: he can reveal himself to his wife and risk social ostracism, thereby possibly losing the life he has built in this Northern city; or he can never speak to her again, but feel guilty about wronging the woman who saved his life.

In the third and final part of the story, he is at the ball he has organized. During an announcement, he indirectly tells the story of how his wife saved his life. He asks the crowd if he should acknowledge such a woman, if she were to come back into his life. They all agree that he should. Now, his friends cannot shun his dark-skinned wife without also being morally culpable. By introducing his wife at the end of this speech, Mr. Ryder preserves his own integrity, while also maintaining his social standing.