TV.com

Susannah Ray thinks she has won her big break--a starring role in Kevin Grant's latest film. She considers herself an exact replica of the character "Abby", who eventually commits suicide in the script.
She is crushed when she learns that Diane Waring, a contract player at Century Studios, has been hired for the role.
Feeling sorry for Susannah, Diane befriends her, allowing Susannah to be her assistant on the set. Susannah continues to rehearse the part, while Diane begin to have strange emotional outbursts on the set. Kevin is concerned about Diane's bizarre behavior, and she is at a loss to explain it. When Diane continues to break down, Kevin considers replacing Diane with Susannah.
Eventually Kevin realizes that Susannah is putting LSD in Diane's daily glass of orange juice, so he banishes Susannah from the set. Diane is afraid that Susannah may attempt suicide,which would be consistent with the character of "Abby". Diane follows Susannah to a cliff at the beach where Susannah is considering jumping. Kevin follows Diane to the cliff and they both prevent Susannah from jumping.
Kevin later tells Sylvia that because of the experience with Susannah, he is changing the end of the script, so that "Abby" will get mental health counseling, as is Susannah, rather than commit suicide.