Print lines from one file that are not contained in another file

I wish to print lines that are in one file but not in another file. However, neither files are sorted, and I need to retain the original order in both files.

 contents of file1:
 string2
 string1
 string3

 contents of file2:
 string3
 string1

 Output:
 string2

Is there a simple script that I can accomplish this in?