What is the secret Leon talks about?!

[nullity]

I found an archived mailing list in which I had asked a question back in 2000... I never did get an answer, so I ask again today:

Does anyone know what the secret is on that one level? Leon says something
like, "Sensors show there may be a secret on this level", in the mission
briefing... and when you are in the hallways, he calls you to say, "...there
is a secret in this area". I remember playing that level for days trying to
find a secret... walking around backwards (ala Order of the Griffon),
shooting up walls, pulling my hair out...