Bob and the team are building a special flat-packed eco-home for Marjorie. When Muck and Benny spot Marjorie's canvas tent and Spud's straw-house, they wonder what else houses can be made from. With their part of the build completed, Muck and Benny go off exploring with Spud. The trio find a river bank full of mud and Muck decides to build a mud-hut. The gang use some old recycled posts to make a frame work. Then they mix up some mud using water from the river and are soon having a huge mud fight! When they find they've run out of mud, Muck collects some more from the river bank. Muck takes so much mud that the riverbank bursts sending a torrent of water heading towards Benny and Spud and completely washes away the mud hut and Marjorie's tent. Muck calls Bob on his Talkie Talkie and Bob springs into action. Using sandbags, rocks and sticks, the team soon patch up the river bank until it can be repaired properly. Muck is very sorry and realizes he's learnt an important lesson - that you can't just build a house anywhere! Muck is especially sorry about Marjorie's tent. Now she has nowhere to sleep! Bob and the team finish the flat-packed house, and Marjorie tells Muck that she's happy to sleep inside the house, even though the interior isn't finished - it'll be like a giant tent. It's been a long day and Muck announces that he's had enough mud for one day.