Thanks to the excellent staff at the Peoria Public Library, I've learned a lot about Walter Donley's disappearance.
According to various articles from the Peoria Journal Star, Donley became unwittingly involved with an organized crime organization based in St. Louis.
On January 12, 1942, two men from St. Louis met with Donley and gave him $15,000. They asked him to be their attorney and requested him to deposit the money in a local bank.
Donley complied, apparently unaware that the money was part of $65,000 taken from a business in St. Louis a couple of weeks earlier.
The stolen money was traced to Donley, who denied knowing it was stolen. He assisted the authorities in their investigations.
One of the two men who met with Donley and gave him the $15,000 was Lawrence Drewer who was high up in organized crime in St. Louis.
This is how Donley became a state witness - he was to be a key prosecution witness in Drewer's trial because Donley could connect him to the stolen money.
On June 1, 1948, Donley was served with a subpoena stating he was to testify in Drewer's upcoming trial. The subpoena was served at 4 pm, and shortly afterwards he called home and spoke to either his wife or to his daughter (reports vary) saying he'd be home soon.
His secretary said that Donley left the office around 4:45 p.m. in the company of two men. I can't find anything that provides a description of these men.
According to a witness, Donley's car was seen parked in the 100 block of S. Bourland at 5 pm. The witness claimed two men got out of the car talking loudly to each other. One of the men was carrying a briefcase and wearing a blue shirt which did not match up with what Donley was wearing that day. The witness was unable to identify the second man as Donley.
The two men rounded the corner and continued walking toward University.