Slugterra S04 E01 Into the Shadows: Back on the Shane Gang (1)

"Slug it out!"

As the Shane Gang returns to the 99 caverns from their Eastern adventure, they find Gateway Cavern overrun with slugs. In the Shane Gang's absence, the Shadow Clan took a different approach to protecting the caverns, putting slugs before the needs of people and it's up to Eli and the gang to restore balance.