Red Alert is a Shareware Wolfenstein 3D mod by Merijn Heijnen released in November of 1999.
The story is described in an included text file as such:
Once allies against Hitler, the Soviet Union and the United States confront each other at the end of World War II. Looming over the postwar landscape is the awesome, mushroom-shaped cloud of the atomic bomb. The"Cold War" was fought on two fronts. In public, it was a series of confrontations and crises. But the East and West also battled in the shadows, as intelligence agents risked their lives to steal secrets. And so it's up to you, as American spy, to infilltrate a Russian KGB-building and to discover a secret weapon depot.