De Armas plays Marta, the nurse of 85-year-old Harlan Thrombey (Plummer), a mystery novelist who is found dead the night after his birthday party. Without giving away too much, Marta becomes the center of the movie when she starts working with Detective Benoit Blanc (Craig), who feels he can trust her because she has a condition that means she’ll vomit if she doesn’t tell the truth. As an immigrant — in a running joke all of Harlan’s xenophobic relatives think she’s from a different country — Marta is also trying to protect her undocumented mother, so she needs to avoid being implicated in Harlan’s murder. Also, when it’s revealed Harlan left Marta his estate, one of the family members tries to blackmail her into giving it up by saying he’ll expose that her mom isn’t in the U.S. legally.