While Detective Ed Brown (Don Galloway) gives a public-service lecture at a local campus, someone plants a bomb. The school is vacated after Brown is handed a bomb threat made from words cut out from newspapers and magazines. U.S. Army Warrant Officer Frank Simpson (Ed Asner) and Sergant Vernon show up to diffuse the bomb. The bomb turns out to be a prank. When the brief-case exploded in their faces it merely spewed out talcum powder.
Back at the bomb-disposal unit's headquarters, Simpson and his assistant, Sergent Vernon, argue over a woman (Darlene) on several occasions. Vernon had been dating Darlene, but Darlene was more interested in Simpson.
The next day another paper-clipped bomb threat arrives. Before the bomb disposal team could arrive, Ironside and Mark find another phony bomb. However, this fake 'bomb' used an explosive cap. The bomb was fake, but the cap could have blown a hand off.
Eve poses as a new recruit to the campus newspaper hoping to find clues to the mystery there. She discovers a ticking case while working after hours. This time, no bomb-threat warning was given. This third 'fake' bomb contained old and 'touchy' dynamite (making it dangerous to handle), but with no explosive cap to set it off.
Eve learns that the campus newspaper editor, Neil Morgan (Philip Chapin), had to work for years on Alaskan construction sites to earn enough to pay his way through university. When later questioned by Ironside, Morgan believed the 'bombs' were being planted by a 'militant leftists'.
Sergent Vernon gets drunk and shows up unwanted at Darlene's apartment. While Simpson helps Vernon sober-up, a forth bomb is discovered under a statue. Vernon is too drunk to assist and stands 20 feet away while Simpson attends to the bomb himself. While dismantling the bomb, Simpson (Asner) thought it was another fake bomb. But it exploded, and ultimately killed him. Turns out it had a 'double-fuse' that Simpson missed on initial inspection.
The forensic investigator noticed that the fourth news-paper clipping bomb-threat note was different from the prior three. It was cut out differently (using a different pair of scissors) and each piece had print on the back-side - the prior three did not. Note a plot blooper here. There were no paper-clip bomb threats mentioned in the context of the third and forth bombs. Yet at this point in the show, it appears there were advance-warning, paper-clip bomb threats for all four bombs.
Ironside suspects the campus editor, Morgan, planted all the bombs. He had worked in construction in the past, making it likely that he had worked with explosives. Ironside believed that Morgan wanted the 'militant leftists' to be blamed for the bombs. When questioned (off camera) Morgan admitted to planting the first three fake bombs, but not the one that killed Simpson.
After remembering that he had seen Simpson and Vernon fighting earlier, realizing that it would take an expert to make a double-fused bomb and noting that Simpson's last words were "why did he do it?" (not heard by the viewer) Ironside suspects Vernon.
When questioned, Vernon tries to make a run-for it and is stopped by Mark. Vernon is charged with murder. Mark concludes that Vernon set the bomb for Wilson to unsuccessful diffuse because 'Simpson took his girl" Darlene.