The Situation:
The final murder takes place near simultaneously with the previous two. The group is split into pairs and are searching the house, Ms. White turns off the power. Chaos ensures.
The Murder:
We get almost nothing to chew on about this murder. In the darkness, the doorbell rings, is answered and the poor telegramist is gunned down. We find out during the subsequent investigation by the group that the girl was the one who had an affair with Prof. Plum, cost him his practice and then informed on him to Wadsworth.
This murder breaks the pattern and to some extent the logic of the movie. The setup of the whole film is that each game piece character kills the person responsible for their blackmailing troubles. By this logic, Prof. Plum should be the one to kill the Singing Telegram Girl. Yet the setup of the movie makes this impossible. All of the other victims existed in the house for the entirety of the movie. Long enough for each killer to get over the shock of seeing their blackmailer and accomplice and then try and put together a murder plan. In this case, Prof. Plum isn't even 100% sure the girl is informing on him, he only suspects. He probably would've figured it out had she been there the whole time but that didn't happen. At no point can he possibly know that she is even coming, let alone make a plan to kill her. When she arrives during the power outage, Prof. Plum is in the basement with Mrs. Peacock and the gun is strewn on the hallway floor. Impossible that he can get upstairs, figure out who is at the door, find the gun, take the shot and return to the basement. No, Plum's murder was spent on Mr. Boddy.
So instead of Prof. Plum logically killing his nemesis, the duty falls to Wadsworth. In one respect that makes sense. Like all the other visitors that have been killed, the Singing Telegram Girl was brought to the house by Wadsworth. Only he knew about it, so he could be the only one who developed a plan to kill her. The question though is why? All during the movie Wadsworth has done nothing proactive to ensure that the group killed their informers. Aside from instructing Mr. Boddy to bring all the weapons, he essentially let the rest of the cast determine how the events played out. The main goals of this passive stance was to allow the game pieces to do all the killing, leaving Wadsworth with no blood on his hands, no troublesome informers left and more information with which to blackmail the group. Killing the Singing Telegram Girl ruins all of that though. Suddenly he himself is wrapped up in a mass murder house, just as guilty as the rest. It damages his ability to blackmail the group as he no longer has informers to their government dirt and they have equal dirt on Wadsworth as a murderer. Wadsworth has ultimately weakened his position.
This murder also adds to the general chaos of the last murder scene. As we know now, during the house searching scene, Plum and Peacock were in the basement and out of the action entirely. Mustard and Scarlett were on the main level, separated. White and Wadsworth were on the second floor, separated and Green and Yvette were in the attic. As they groups were searching, Ms. White goes down to the main level and turns off the power. Then, Wadsworth and Yvette go to the main level as well. So now we have Mustard, Scarlett, White, Wadsworth, Yvette, and the Off-Duty Policeman are on the main level and the Telegram Girl is on the front step. Additionally, Scarlett and White have to get their weapons from the same cabinet while Wadsworth has to get the gun, in the dark, from the mess in the front hall which is in plain sight for everyone. Weapons acquired, Scarlett has to get to the library, White has to get to the billiards room, Wadsworth has to stand in front of the door waiting for the bell to ring and all of them have to do this without being seen by each other or the wayward Col. Mustard who is doing something. Maybe just hiding somewhere. Even in the dark, that is a lot of movement by a lot of people in relatively short time and confined spaces. It also assumes that Mr. Green, who we know is an FBI agent investigating the blackmail, is unaware or has chosen to do nothing about the fact that Yvette has split from him. The attic didn't look huge so its very hard to believe he was fooled in any way. Ultimately Green played no role in the final burst of action.
Conclusion:
Like Yvette, the Singing Telegram Girl just had to be killed so that the movie could get to the fun part. The lack of a cohesive plan by Wadsworth finally reaches its apex as he is forced to ruin his own plan by killing the Telegram girl. I understand that the movie needed Wadsworth to do something evil so that there could be the big shocking reveal at the end that he was actually Mr. Boddy. If they couldn't figure out a way for Prof. Plum to kill the Telegram Girl, they should have left her out completely. In that situation, all six game characters would have killed someone and Wadsworth could have revealed his true identity some other way and left his master plan intact. Of course, that would leave Wadsworth with one informant left operating in the world. Maybe they should have just found a way to get Plum's informer into the house and had him kill 2 people. Would've made more sense.
Up next:
Murder #8, the final overall death. No mystery but interesting in some ways.
Up Later:
The phone call from J. Edgar Hoover and the interruption from the beatnik have to be addressed but only after the main mystery has been unraveled. Soon.
Recap:
Wadsworth: 1 murders
Peacock: 1 murder
Green: 0 murders
White: 1 murders
Mustard: 1 murders
Scarlett: 1 murders
Plum: 1 murder
Wadsworth: 1 murders
Peacock: 1 murder
Green: 0 murders
White: 1 murders
Mustard: 1 murders
Scarlett: 1 murders
Plum: 1 murder
Mr. Boddy: dead
The Cook: dead
Yvette: dead
Stranded Motorist: dead
Off Duty Cop: dead
Singing Telegram Girl: dead