The fix for this example is relatively simple - the first mission we give should not be the first that gets completed but the LAST. We tell the player upon arriving that the goal is to rescue Gibbs and we show them his place locked in the tower. After that the player is free to explore and find all the elements that block them from getting to that objective before attempting to overcome them.

This flow is supposed to represent three missions which each unlock part of the way to the main objective, but remember these don’t need to be literal gates, nor do they need to be sequential. The unlock might be a tool or even a piece of knowledge the player needs to progress.