The Incredible Adventures of Van Helsing III

When you arrive in the Secret Lair, you will find the Command Post directly above the teleporter. Here you will send your four captains on various missions. Try to choose a captain based on the mission description and the tips they give for completing it. Often it will be fairly obvious who will have the best chance of success. Each mission takes a number of real-time minutes to complete (must be in-game for the counter to work - sadly you can't start a mission and exit the game then come back and have it complete), so check back often and continue to send people out to complete the missions. They unlock at specific points in the story, so don't worry if you don't have any missions to select for a while. The last two unlock during the game's final story mission - make sure you teleport back to base right when you get the notification and do them.

Note: I failed the final two missions and still unlocked the achievement, so that doesn't seem to matter.