For example, a young teen enters a grocery store. As he’s paying for items, armed men enter to rob the store. Shopkeeper doesn’t cooperate and gets killed. The young teen is a witness. (A very basic and familiar story beginning, right?) Armed men decide to kidnap the young teen and decide to hold him hostage in hopes they will get paid for his return. Except no one turns up looking for him. (This is the beginning of your twist and originality).
For example, ‘Wedding Crashers’ can be described using only the title. It’s a film about people who crash a wedding. The only elaboration needed would be to explain how these wedding crashers are different from any others. What’s their story? Do they have a motive?