The first fire was on 16th Street and displaced 13 people. Half an hour later, an empty building on 17th Street went up in flames and another blaze began on the 2200 block of Market Street. Then there was another fire Friday morning.
James Bolton owns the two flat building on the 400 block of 18th Street, where Friday's blaze erupted. He operates a barber shop on the first floor. His patrons Thursday had told him about the other fires in the Castro.
"I just thought to myself 'Damn, a loose fire bug in the city,' and I was just thinking, 'God, that could be this place,'" Bolton said.
Shortly after 4 a.m. someone tried to burn down the building by igniting a large piece of plastic in front of the doorway. Fortunately, tenant Mary Slyvia smelled the smoke.
"The closest thing I had was the tea kettle off the stove so I just grabbed that and filled that with water and came down," Slyvia said.
Sylvia doused the flames and then woke up the Boltons, who live in the upper flat.
Sandra Bolton says Sylvia saved their lives.
"If the neighbor didn't find out what would happen, we were all in deep sleep," she said.
Not far away, tenants were back in their apartments on 16th Street, looking for belongings that can be saved.
"The place is just wiped out, gutted," tenant Rick Kennan said.
Kennan lost almost everything in the fire that raced from the front door up the stairwell, enveloping the upper flat where he and others live.
Ying Hsaio lives in the bottom flat. She has a hard time grasping what happened.
"Angry, pretty angry; I woke up just sad and angry today," Hsiao said.
Fire and police investigators are trying to see if the fires were set by the same person.
Many residents say there could be only one motive.
"It's the Castro; I'm sure people have feelings against people who live in the Castro," Castro resident Trina Chow said.
Police are asking residents to be vigilant.
