Plot hole: When Diana turns up at her director friend's house she finds it crawling with cops as his girlfriend Christie has been murdered and the house is now a crime scene. She explains she lent Christie a coat and is there to pick it up - and a cop helpfully finds it on the floor and hands it to her. Are we to believe that a homicide policeman will hand over an artifact from a murder scene to an unidentified woman without making any attempt to confirm her identity, or even if the coat is even hers!? They don't even ask.
Plot hole: When Fitz-Hume and Millbarge disguise themselves as aliens in order to distract the mobile launcher crew, where exactly did they get the foil they are wearing? Except for the satellite dish Millbarge wears on his head, no parts of their code transmitter can have been used or the thing would be of no further use, and it is very unlikely that either of the two spy groups brought any of the foil along.
Plot hole: After Frank and Freddie accidentally release the trioxin gas, there are several shots of the gas entering a return air vent and traveling through the heating, ventilation and air conditioning system belonging to the warehouse. Finally the gas exits into the freezer directly on to a hanging cadaver. This room was previously confirmed as a freezer and would have had its own self contained refrigeration system with its own ventilation system. Typical freezer doors also seal as they close. The cadaver would have never come into contact with the trioxin gas and would have never reanimated.
Plot hole: When Miss Scarlet tells the other guests, they can pay her in government information, she forgets Mrs White is the only to have no connection to the government and thus can't pay her that way, nor does she have any more money like the others.