especially if it helped people, benefitted people, if he could make money off of an idea. >> reporter: hal fischelorked with bill on an early phase of the machine. it was after fischel left the company that the money came rolling in. fischel thought his contribution to the invention deserved more what he got, so he sued bill mclaughlin, his former friend and partner. here's the thing. it was just two weeks before the murder that the courts decided for bill. any day, he was to get the $9 million he and fischel had been fighting over for years. so was it a revenge killing? sounded at least plausible. except for something the killer left behind, something fischel didn't have access to. no, it wasn't dna, not fingerprints. something more mundane than that. >> when we got here, the door on the right was open and there was a key stuck in the lock right here. in addition to that, there was a key on a mat laying right next to the door here. >> reporter: two keys. two clues. one was a brand new copy of the front door key. the other was a key to the community pedestrian gate, not a copy. >> those are huge,