Last Saturday night, a group gathered at the Flamingo Estate in the Eagle Rock neighborhood of Los Angeles to meet the spiritual adviser Carissa Schumacher.

At the front of an open-air room, a seat awaited Ms. Schumacher under a large floral arch. After guests, including the actresses Jennifer Aniston and Uma Thurman, filled the rows of chairs, others moved to the floor. Andie MacDowell reclined on a rug among a heap of pillows. Ms. Schumacher was supposed to appear at 8:30 p.m. A gospel choir sang while everyone sat around and glanced at Ms. Schumacher’s empty chair and at each other.

Since 2010, Ms. Schumacher has worked as a medium, meaning someone who receives messages from people who have died. She doesn’t have a website and is often booked months in advance. Her prices are another obstacle, with sessions priced at $1,111 per hour. (She likes the synchronicity of the number.)

Ms. Schumacher might fall under a category of so-called New Age practitioners. But spiritualism — the belief that the living can communicate with the dead — is very old, its popularity surging in times of high mortality rates: in the Victorian era, for example, and after major wars in the United States and Europe.