The fire broke out early Saturday morning on Nashua near West 13th Street.
Two neighbors say their dog started barking in the middle of the night, waking them up.
They looked outside and saw smoke coming from the duplex next door, so they rushed out and called 911.
The owner of the duplex wasn't home, but the neighbors said they knew he had a cat that was stuck inside.
Firefighters moved in and recued the cat, who is now doing fine. Officials say the kitty was able to find a safe place to hide until they arrived.
The duplex was destroyed and the investigation is ongoing, but no injuries were reported.