Robert Johnson was an influential blues musician.
Johnson in the Timeless Universe
In the original timeline, Robert Johnson and Don Law record an album at the Gunter Hotel in Texas on November 23, 1936. This album contributes to such cultural revolutions such as rock and roll music and eventually the counterculture of the 1960s, the civil rights movement, the fall of President Richard Nixon, and the end of the Vietnam War.
In the altered timeline, a Rittenhouse agent attempts to murder Johnson as he records the album. The Rittenhouse agent is killed by Garcia Flynn before this can happen, but it still causes Law and Johnson not to record the album, because Law thinks Johnson is cursed, and Johnson believes he is too, due to his deal with the devil. Johnson leaves the room without Flynn, Rufus Carlin, Connor Mason, or Lucy Preston noticing.
Rufus and Mason later reunite with Johnson as he leaves, and Mason eventually convinces Johnson that he knows his sister, Carrie Thompson, and offers to drive him to her bar. This was a plan to reunite Johnson and Law at the bar, instead of the hotel like the original timeline. Later, when Rufus tries to get a hold of Flynn and Lucy at the Gunter Hotel, Mason and Johnson talk to each and find they both have made "deals with the devil," Mason in a more metaphorical way, however.
When they arrive at the bar, Johnson spends time with friends and other notable musicians such as Muddy Waters, Son House, and Bessie Smith. The mood changes however, when Rittenhouse agent Betty comes to the bar and tries to kill Johnson again, but is killed herself by Mason. After a pep talk by Rufus, Mason is able to convince Johnson to persevere, and record the album at the bar.
Robert Johnson at Wikipedia