Police are questioning a 26-year-old man over a Shoalwater incident in which a woman was held captive for four days and assaulted.
The man was taken into custody after a vehicle stop in Kwinana about noon today.
No charges have been laid.
It is understood the man does not live at the Hawker Street house where the alleged incident took place between Thursday and Sunday.
Police allege the woman was held against her will and assaulted. There were reports she also had chemicals thrown on her.
She was taken to Rockingham Health Campus for treatment.