She arrives at the party , but is stopped by the Liars , who left the barn to come and protect Alison .
The Liars head to their prom party in Spencer 's barn while Alison goes to the official prom .
Alison arrives at the party , but is stopped by the Liars , who left the barn to come and protect Alison .
The Liars head to their prom party in Spencer 's barn while Alison goes to the official prom .