Hawkeye and Margaret get "volunteered" to go to another MASH unit to teach valve replacement. Unfortunately, before they arrive the unit is forced to bug out. The two start to drive each other crazy. Margaret has received a letter from Donald that is obviously not to her liking. The two have several close calls and find themselves in a hut with mortar shells falling all around. Margaret finally confesses what is in the letter. Hawkeye shows great sympathy toward her, even though she has not been very kind. Meanwhile, back at the 4077th, everyone is crazy to hear news of them. Things are still up in the air as the episode ends with one rather remarkable event added in.