Senior Sangjun Hornewer scored just 45 seconds into the game but Lake Forest was defeated 2-1 at Knox College on Sunday.
It was the fourth goal of the year for Hornewer.
Knox tied the game at the 13:58 mark and the score remained 1-1 for the rest of the opening period.
The home team pulled ahead at 61:52 and held on for the victory.
Lake Forest is now 7-5-3 overall this season and 2-2-2 in Midwest Conference play while the Prairie Fire improved to 11-4-2 overall and 6-0-1 in the league.