Ruth was a scientist working for Rudolph Metz.
When Caleb Taylor was saved from a freezing chamber -200 degrees by the visitor Willie, who was freeze resistant from the ice chamber, Willie's skin tissue was on Caleb Taylor who was brought to a L.A. hospital.
Steven, the visitor commander of the plant, noticed Willie was missing some tissue skin. Under orders from Diana, Steven followed Caleb to the hospital and found out Ruth treated Caleb and took the visitor skin tissue home to reserch in Metz's office the next day. Steven placed a homing device on Ruth till night time and, after Julie Parrish dropped Ruth at her mansion home, killed Ruth with a laser gun before she could take the visitor tissue to the lab and learn that Willie was a reptile.