First, after six months of investigating, the police had exhausted all leads and given up on finding Tom Grunemann. So, it makes no sense the murderer Peter Cable - a person desperate to hide his crime - would initiate and finance a renewed and reinvigorated investigation by a highly-motivated Klute.
Second, it turns out that Klute’s whole NYC investigation and tracking down missing prostitutes was unnecessary. The case was actually solved back in Pennsylvania by comparing the typewriter font on the obscene letters to the typed correspondence from Grunermann’s associates including Cable. Basically, had Klute taken this obvious step first, Arlyn never gets added to the list of people murdered by Cable
Gruneman's wife also wants to hire Klute. She's with Cable at the beginning of the movie when they meet with Klute. She doesn't believe Gruneman wrote the letters to Daniels. Cable probably volunteered to pay Klute so that he'd be in the loop and would know what was happening his investigation.
The thing that didn't make sense to me at all is that Cable would plant the fake obscene letter in Gruneman's office. He's hoping they'll think Gruneman is mental and might have run away, which the police do.
The thing is, that leads everyone directly to a call girl that Cable saw once and beat up. Not only that, but he also saw Page, who knew both Daniels and McKenna. His entire plan hinges on Daniels not being able to remember what the person who beat her up looked like at all, and that Daniels won't have some information that'll lead to Page, who also knew McKenna and had done "freaky" things with Cable.
Someone explains this away by saying that call girls like Daniels see a lot of Johns, so they forget them quickly. It's ridiculous that she would completely forget the face of a John did that to her though, not even well enough to say whether it was Gruneman or not. Daniels can remember that she was beaten up two years ago and other things about the incident. And Page can remember some things about him, and that he was older, but when Cable plays the tape of her murder, she doesn't recognize him right away, even though he beat her up too.
I don't think so. I'm sure call girls remember some of their more unusual clients, especially the ones who are violent.
Very good points Haslet. It was completely counterintuitive for a guy trying not to be caught for murder to send the investigator to plant evidence that would lead to a witness who would connect him to the murder. I also think call girls are the type of prostitutes who get paid by their customers to remember them and Daniels had a high probability of remembering even had he not beat her up.