Beauregard ("Beau", for short) was kept chained in the attic by his mother when his family lived in the Murder House. He was smothered with a pillow by Larry Harvey (at Constance's request). However, Constance refuses to admit this, instead saying he died of natural causes. His spirit is currently trapped within the house's attic. Constance was going to be charged with child neglect, meaning Beau would be institutionalized by Child Protection Services, and she couldn't bear the thought of "them taking away" her family. It is still unclear if she neglected one or all of her children. It was, however, 1994, the year in which Tate committed the Westfield High massacre. Later on, Constance visits him and tells him they will be separated because of Joe Escandarian's plan to tear the whole house down.
He is afflicted with craniodiaphyseal dysplasia and seems to suffer a mental disability, as well. He is very friendly in all of his encounters with other people, despite the horrific conditions his mother has kept him in.
Home Invasion - Beau's red ball is seen rolling out into the basement after playing with Adelaide.
Open House - Violet sees him while in the attic. She is startled by him, although he seemingly just wanted to play with her, since he just rolled his ball towards her.
Rubber Man - Violet plays with him in the basement and is found by Ben, who asks who she is talking to, though she says no one and the two go upstairs. Hayden also rolls the red ball to him while sitting on the basement floor. Vivien later sees the red ball roll towards her in the hallway, and picks it up, though Beau is nowhere to be found.
Afterbirth - Beau jumps from the attic and scares Stacey Ramos. It is unknown if he did this by coincidence or if he was involved in the Harmons' plan to scare them away.
Beauregard Langdon: "Nnnghhh!"
Beauregard Langdon: "Play!"
In the episode "Home Invasion", Adelaide is seen playing with a ball in the basement, and the ball mysteriously returns to her. It was the same red ball Beau passed to Larry and later Violet to play with him in "Open House". After these three instances, it seems that Adelaide was just playing with her brother Beau, and that Beau can appear in both the attic and basement.