Serial killer type murder happens. The next day a storage unit goes up for auction, 30 days after payment running out. Inside is clear information regarding the victim, but placed there a decade ago (they paid 10 years up front).
Cops then identify which storage units will be up for auction the following weekend, and there are three. Each is overflowing in junk. When they finally find a pivotal clue, they get there too late and a second victim is dead, exactly 24 hours after the first.
Then auctions for the weekend after that, there are ten. Seemingly the same person rented all of them. They are too late again.
The cops are already checking those for the weekend after, and the weekend after that. There are 23 and 36 respectively. All full of stuff. The police are overwhelmed with trying to deal with all the possibilities.
They fail with the fourth, and there is no link between any of the first four victims, or the clues left in the storage units.
With the 36 units due for auction in four weeks, and the daily deadline approaching, one cop recognises something about themselves. Turns out that all 36 units each have one clue about a cop who worked in that precinct 10 years ago. All 36, past and present officers, are targets.
Make your own ending!