First, you'll have to complete the main story mission, Power Up The Gate, so that you get access to Spooky Swamp, and then you'll need to do Re-Haunt The Swamp, given to you once you reach ...
The Crew’s search goes horribly wrong when, in the middle of the Lake Tranquillity swamp, Bert is snatched away by the Spooky! They track the culprit, a giant Swamp Monster, to its lair ...