Part One: A local vendor has set up his cart in the middle of the camp's compound and Potter has a Korean liason tell him he needs to leave. Before he leaves, Potter sees a lighter he wants to buy. The vendor offers five dollars, four if he can stay for a going-out-of-business sale. Potter offers three and he can stay for another hour. He then notices a spirit post that the locals have put there to help ward off bad spirits and has Radar remove it. After he does, Potter's nre lighter stops working and a local crashes his bicycle into the vendor's cart. Radar mutters to himself, 'I knew it, I knew it.' In the Swamp, Frank is putting on a rather aromatic cologne. Hawkeye and BJ steal it from him, and in trying to get it back, he breaks his mirror and blames Hawkeye for it. Radar comes in to tell the doctors that wounded are coming in because the PA system is not working. In the OR, things go wrong. Margaret's finger winds up in a clamp, light bulbs go out, a blood pressure gauge gets stuck, and Potter clips his own finger. Everyone also comments on Frank's cologne. BJ finds his latest patient is a repeat customer: Cpl. Marsh, who got hit in a leg two months earlier. He's back after getting hit in the same leg. He tells Father Mulcahy that he lost his St. Christopher medal and asks to get it replaced. Klinger drops a light bulb and scares Frank; he says Klinger did it on purpose. Then Margaret squirts saline on him. She says the date is Friday the 13th. The lights flicker on and off and Potter says the locals think evil spirits are around. When Mulcahy drops BJ's table of instruments, BJ says they are jinxed and Potter says that nothing wil go wrong--except the lights when they go out completely. Later, Marsh is going home early and tells BJ that he never got his medal. He offers to go and get it, but Marsh says it can wait until he gets home. Radar gets lighter fluid for the Colonel's lighter. He asks Radar when the PA will be fixed and Radar tells him the electrician is 'resting' over at Rosie's Bar: he was fixing their wires got shot through the wall. Mulcahy comes in and asks Potter how he can get Marsh his medal; Radar tells him that the driver of the next ambulance can get it to Marsh at the EVAC hospital. Radar leaves and Klinger then comes in to repalce a light bulb. He tells them that bulbs are going out all over camp and that bad luck is spreading to poker games and his nylons. He shows his blue bead which he believes also wards off evil spirits. Radar comes in with a horseshoe to put on the wall. He says he won it of Igor in poker. Potter says he has never believed in horseshoes and good luck, but he thinks it will go with all his horse picutres. Then another ambulance comes back in. It turns out that Marsh is on it and is hurt again. The driver says that an old Korean man ran in front of the truck and he hit him and wound up in a ditch. Frank insists that the old man is a 'whiplash hustler,' a local who tries to get hit and sue the Army for money, so he doesn't want to operate on him. His granddaughter, Kyong Ja, says it was deliberate, but not for that reason. She says her grandfather believes he was being followed by evil spirits, so he ran in front of the truck to scare the spirits away. Mulcahy says that Koreans do that and hope the driver can avoid them. Hawkeye brings him into pre-op over Frank's objections, but the old man does not want to be treated there; Kyong Ja says he believes evil spirits are there and wants to leave. Hawkeye tells her that he will die if he doesn't get surgery, and she says that he wants the evil spirits to be exorcized before he will allow being treated. Hawkeye does a fake one which brings Frank out. Kyong Ja says that it must be done by a priestess which is a mile away. Hawkeye tells Radar to go get the priestess and Frank orders him not to. After a back-and-forth, Hawkeye tells Radar to go and he leaves with Kyong Ja. Frank calls Hawkeye the most unmilitary man in the Army, to which Hawk replies, 'Thank you.'
Part Two: Frank, Hawkeye and Mulcahy are in Potter's office. Frank protests bringing the priestess in as against regulations. Hawk says he just wants to reassure the old man so he can operate. Potter says yes and he might have her exorcize all the evil spirits off the compound. When Frank says he can't do it, Potter says he can and won't apologize to him, but to the Padre. He says that he can't wait to see what she will do. In post-op, BJ is sitting by Marsh's bed. When Margaret says he doesn't need to, he says that he wants to see the look on Marsh's face. When Marsh does wake up, BJ explains what happened. Marsh says that it's the third time, and BJ says that one more and he wins a solid gold jeep. He tells Marsh to look him up after the war and for old times' sake, he'll take out his appendix. Later, the priestess shows up and starts doing her ritual in the compound, attracting a crowd. The old man watches from his stretcher as she uses bells and a fan in her dance. Later, as the doctors prepare for surgery, Potter and Mulcahy sit in to watch. Frank and Margaret both object to the priestess's presence. Wearing a surgical mask, she enters and does a similar dance to the one in the compound. Margaret likes her outfit, but Klinger calls it 'too pushy.' Mulcahy calls her a cross between a bishop and a bullfighter. The old man is them brought in and she leaves. Frank calls it ridiculous and that it did no good. The PA announcer then announces that wounded are coming in. When Hawk says that he though it was broken, the announcer then announces that the PA is working again. Margaret tests a blood pressure gauge and finds it works. The light bulb then comes on. Frank says it probably won't happen again, then knocks wood. Hawk tells Kyong Ja that he will visit her grandfather in a week to check on him and not to run in front of cars unles they are parked. She gives him a string of bells as a gift, not for exorcism, but for decoration. He says he'll use it to chase away the blues, or the olive drabs. Potter insists that someone check out the PA system, then finds that his lighte rworks. He orders Radar to put the spirit post back; Radar says he already did. Marsh is loaded into another ambulance. BJ tells him, 'This is it.' When Marsh says that he said that before, he says, 'But this 'This is it' is it. Mulcahy then gives Marsh his St. Christopher medal. The truck leaves, then stops and honks the horn. Another Korean on a bike rides by. Beej says, 'St. Christopher gets all the breaks.'
Epilogue: Frank is trying to get his radio to work. Hawkeye says that the evil spirits hate radios, and BJ tells him to use his bells on them. When Frank says they won't work and Hawk wants him to bet five dollars that they will. Frank makes it ten. Hawk then shakes the bells and moans and nothing happens. Radar then comes in to tell Frank that the Colonel wants to see him about the duty roster. Frank insists that Hawkeye pay off, but he wants another try. He shakes the bells again and the radio comes on. Frank reluctantly pays off and leaves. Radar wonders how it happened. Hawkeye says all you have to do is shake the bells a few times, and BJ says that you also have to put the plug back in.