Eloise was the half-sister of Ernest Cobb. She was born four years after Cobb and was raised by their mother. She learned of her brother's existence for the first time when he visited their mother when Eloise was 16. Unbeknownst to Eloise, this meeting would later trigger Cobb to murder because of the anger and jealousy that he felt towards her because she had been raised by their mother while he had been given up and raised in an orphanage. This made Eloise the true target of Cobb's murders.
After Cobb was sent to Alcatraz Prison Eloise attempted to contact her brother. However as Cobb didn't have a list of people who could contact him he never received her letter. Instead it remained in storage at Alcatraz until 2012 when it was discovered by Diego Soto and Rebecca Madsen.
In her letter she wrote:
- 'Dear Ernest,
- You probably don't know me but I was there the day you came to find your mom. Who's my mom to. Which, I guess, means we're brother and sister. I'm sorry she was unkind to you. She's never been one for surprises. I read about you in the paper, being in Alcatraz and all and I figure you're probably lonely. I hope it'll be okay if we're pen pals because I always wanted a big brother to look out for me.
Cobb didn't learn about the letter or his sister's attempts to contact with him until 2012 when he was confronted by Rebecca. Eloise died in a car accident in 2003, nine years before Cobb reappeared at the age of 75.