Tonight on Pretty Little Liars, the police took everyone to jail! Unfortunately, it was not for any crimes on their part. Instead, some questionable evidence and a false accusation landed the girls in hot water. To think, it all started with an innocent frat party . . .
In the past, Alison got the girls some primo fake ID's so they could go to frat party. While checking out the surroundings, the girls spotted Spencer's sister's boyfriend taking a very drunk upstairs. Alison then suggests the girls split up to cease the frat party night.
For the most part, the girls enjoy the party. However, the aforementioned very drunk upstairs girl ruins the fun by falling/ being pushed downstairs to her doom.
In the present, the girls find a bloody trophy that might correspond to Alison's fatal wounds. After some debate, they bring it to the police. When the police come to school the next day, they surprise the girls with the nature of their business and the results of the evidence.
Criminal Masterminding 101: Always plant fake rat blood evidence.