Hollywood private eye Becky Altringer claims Evi Quaid employed her services in June (09) after she and her husband Randy Quaid received a death threat against them.
Legal papers filed in Los Angeles Superior Court state Altringer was hired "to investigate possible insurance fraud and (a) threat to their lives".
According to RadarOnline.com, Evi allegedly told Altringer to quiz the cast of Lone Star Love in an attempt to find out who was responsible for the threats.
The investigator claims, "(Evi) demanded that I harass the individuals who were part of the Broadway play, Lone Star Love, because they signed a document making allegations against Randy Quaid."
Quaid, who also starred in Brokeback Mountain, was booted from the Actors' Equity Association in February 2008 after he was accused by all 26 members of Lone Star Love of physically and verbally abusing them.
Evi is thought to have suspected one of Quaid's former colleagues of making the death threat.
But the professional relationship between Altringer and her clients soon soured and she quit working for Evi and Randy Quaid at the end of June (09).
Altringer, who is also suing the couple for $19,000 (£12,665) in outstanding fees, went on to call into question Evi's state of mind after reportedly witnessing her snort a white powder, which the actor's wife claimed was migraine medication Demerol.
She states, "I observed Evi's paranoia increase and she was convinced someone was going to murder Randy and then Evi to make it look like murder/suicide. I was concerned because of the Demerol use and Evi was becoming mentally unstable."
A ruling on the restraining order has yet to be made.