About sixty miles from Austin, Texas, Mike joins bat biologist Jim in front of Bracken Cave. This cave is the home to forty million bats. He is briefed on the dangers of entering the bat cave, such as the high level of ammonia and carbon dioxide along with flesh-eating beetles. The pair walk down toward the cave entrance and put on their protective gear.
Mike points out the ankle-deep levels of bat droppings and explains that Jim enters the cave several times a year to ensure that the enormous bat population is not affected by outside forces. They're very vulnerable and he wants to make sure the population isn't declining. As they venture further into the cave, Jim mentions the "rain" or bat urine falling on them.
Jim captures a bat for inspection and explains some biological information about the bats. They eat an amount equal to their own body weight each night. They soon make their way toward the cave's exit and Mike realizes that it's easier to enter the cave rather than exit it. As Mike is walking out of the cave, his boot ends up stuck in guano. He slowly works his way out. They make their way out of the cave and get cleaned up. Jim explains that when nightfall approaches, millions of bats begin exiting the cave in a process which takes several hours.
Keeping on the theme of bat biology, Mike then travels to a bat rehabilitation clinic and meets Barbara French. They begin by fixing the bat's food - blended mealworms. They divide the "mealworm smoothie" and Mike has a taste.
The pair then travel to the "bat hospital" where Mike will feed a bat named Peaches. Barbara takes Mike to another bat who has some dental problems and needs her teeth brushed. Using magnification he scrubs the bat's teeth with a small wire brush. Barb explains the complexity and variety of signals bats use, along with calls they exchange in bat language. After that they enter Barbara's home where some of the larger bats are housed. She shows Mike how to scratch Zoe, a fruit bat.
Next, Mike apprentices with Jim, a printer by day, mud hunter by night, who provides rubbing mud applied to baseballs used in every major league game since the 1950's. Mike is blindfolded and taken to a secret location Jim uses to acquire his mud. Mike begins by shoveling and scooping the mud into buckets, but Jim is quite particular about his mud quality and consistency. If you go too deep, the mud gets too sandy and smelly. After some time in the mud, the pair leave the coastal inlet with their buckets full and travel back to Jim's processing facility at his home.
Jim begins sifting the mud through a screen to get the debris out. He explains to Mike the history of the mud and how it came to be used in Major League Baseball. In the 1920's a hitter died when a pitch slipped from the pitcher's hand and hit him in the head. Umpires then looked for a way to make the ball more grippable for the pitcher. Hence, the mud farmer is born.
The mud is then put through a second strainer and Mike works it over with his hands. Jim then adds a secret ingredient and lets it sit for two weeks. They then package the mud in three pound containers for shipping to every major league team in the U.S.
Veteran's Stadium is the next stop for Mike where he goes to talk to the relief pitcher for the Philadelphia Phillies, Dan Plesac, about the use of Jim's mud in baseball. Later, he talks to Dan, the umpire's attendant/assistant equipment manager who is in charge of dirtying up the brand new baseballs. They begin rubbing the mud into ten dozen baseballs and make ball jokes along the way.
Finally, Mike travels to Pacific Coast Seafood where he gets an inside look at fish processing. He first sees professional filleters whose job description is nothing more than filleting the fish that come through the line. Mike dons his protective gear and watches Renee demonstrate how to fillet the fish. Mike is unsuccessful at filleting his first fish, so he moves onto tuna. He is somewhat more successful at the tuna and they move on to a skate and then an octopus.
Another portion of the processing is where the fish that are not used are fed into a grinder. The resulting "fish milkshake" is pumped into a tanker truck. Mike accompanies the truck driver where they deliver the fish goo to a company called Bio-Oregon. Here they process 50 million pounds of fish by-products a year. At the plant the ground up fish waste is turned into fish food, fertilizer, and fish meal among other products.
Mike pumps the fish from the truck into a 50,000 pound holding tank and then later to a decanter where the liquid is removed. No part of the fish is wasted. Oils are separated along with the fish bones and the remaining substance is a powder. Dried blood is then added to that powder to create fish feed. Mike mixes the powders and other ingredients into a dough-like material. An old pasta maker is used to form the fish food pellets. The pellets are then dried, bagged, and shipped out. Mike ends the episode feeding some fish in a pond.