Sarah MacDougal is the chief engineer of the Enterprise-D during the Tsiolkovsky infection, struggling to regain control of main engineering after Wesley Crusher locks her out.
Sarah MacDougal appears in The Naked Now, one of several officers shown as chief engineer during the ship's first year, before Geordi La Forge takes the post.
When the intoxicating infection carried from the SS Tsiolkovsky spreads through the crew, she is lured away from engineering by a faked order from the captain. Wesley Crusher then seals himself inside behind a force field, and her assistant Jim Shimoda, also affected, pulls the isolinear chips from the control systems.
With a fragment of a collapsing star heading for the ship, MacDougal works to cut through the field and then helps Riker and Data restore the engines. Data's rapid replacement of the chips, and a tractor beam trick devised by Wesley, buy the time needed to escape.