The Engineer is an unnamed character in Syphon Filter: Dark Mirror, he was one the few engineers left to live while Red Section were trying to collect data on Dark Mirror.
Syphon Filter: Dark Mirror
The unnamed engineer first appeared when Red Section mercenaries broke into the head of ----- office only to find the Engineer working by they take him hostage in hopes of restoring power and retrieving the information on Dark Mirror. Gabriel Logan eliminates his captors and assists him in restoring power to the plant. Logan then escorts him through the complex with him assisting by disarming employee security devices and reactivating power supplies. When Logan and he finally clear the sectors out and reach "Sector D" He states that he has no clearance to enter Sector D, but there is a ventilation shaft to enter. He boosts Logan up into the shaft thanking him once more stating he's on his own. It is most likely he escaped the complex.