Invasion of the Body Snatchers (1956)

In a small town, Dr. Miles Bennell discovers bizarre cases of people believing their loved ones are impostors. When bodies resembling his friends emerge, he realizes a sinister truth: the town is being replaced by emotionless duplicates grown from giant alien pods. With the invasion spreading, Miles and his ex-girlfriend Becky struggle to evade detection and warn the outside world before it's too late, racing against time to stop the insidious takeover.