The HSB4-update.exe file you have requested: Modifications / Hidden Source / Hidden: Source Beta 4 Client Update - 14.81mb is not available. Perhaps try browsing all files for the game Half-Life 2 and upload any files you want to share or are missing. This is the only information we could locate:
In "The Hidden", players choose the role of either a near invisible killer, Subject 617, or one member of an Intercept squad who have to capture him, I.R.I.S. In the simple but challenging gameplay of an 'one against all'? mode, Subject 617 creeps/sn This is a client update for Hidden Source - apply it over the top of an existing Beta 3 install.