A lieutenant in the Enterprise-D engineering department who works alongside Reginald Barclay and appears as a musketeer in Barclay's holodeck fantasies in Hollow Pursuits.
Lieutenant Duffy is one of Geordi La Forge's engineers aboard the Enterprise-D in 2366. He appears in the third-season episode Hollow Pursuits.
He is working with Barclay on a failed antigravity unit when the first of a string of odd malfunctions occurs. Later a transporter test he is involved in goes wrong, and he is one of the crew members affected as the mysterious contamination spreads around the ship.
The cause is invidium, carried from broken medical containers on the hands of the engineers who handled them. Barclay works this out with La Forge's team in time to stop the ship tearing itself apart at uncontrolled warp speed. Duffy also turns up in holographic form in Barclay's private programmes.