Het Geheim

According to the various sources there appears to have been a number of plays by this name.

Het Geheim by Vulpius

Performed on Tuesday 12 June 1855 by Door Yver Bloeit de Kunst in the Garrison Theatre, and credited to "the author of Rinaldini" - i.e. Vulpius) Also performed were De Helleveeg (Loosjes) and Het Groot Ballet. The evening was in support of the "Patriotic Fund" for the Crimean War. The production was possibly repeated on 28 June.

Sources

F.C.L. Bosman, 1928: p462-3

Het Geheim by François Benoît Hoffman

A comedy with songs. Written in French by François Benoît Hoffman (1760–1828) and translated into Dutch by Pieter Gerardus Witsen Geysbeek. Published by Abraham Mars (Amsterdam), 1801.

Sources

http://books.google.co.za/books/about/Het_geheim.html?id=holWAAAAcAAJ&redir_esc=y

Het Geheim by A de Bruine.

The last production by Door Yver Bloeit de Kunst under the leadership of the 71 year old Johan Combrink, at the Good Hope Theatre 4 June, 1910. Boonzaier wrote a devastating criticism of what was apparently a ludicrous melodrama, badly presented, thus it was most probably a Dutch version of the Vulpius text.