Blue Beetle centers around a powerful artifact known as the Scarab, which fuses with its host at a cellular level, granting superhuman abilities and nearly indestructible armor. Named Khaji-Da and possessing its own will, the Scarab chooses worthy hosts, making activation difficult for most people.

Decades prior, Dan Garrett found the Scarab and became the first Blue Beetle. He later mentored Ted Kord, who created advanced weapons based on the Scarab's research, becoming the second Blue Beetle. Ted's sister, Victoria, aims to advance Kord Industries using deadly technology, leading to Ted's disappearance.

In the present, the Scarab chooses Jaime Reyes as its host, making him a target for Victoria. After a tragic attack on Jaime's family, they unite to rescue him from Victoria's clutches. During the struggle, the Scarab's alien code is transmitted to Victoria's weapons.

The climax reveals that Carapax, Victoria's enforcer, has merged with the Scarab's code, gaining immense power. However, Jaime's connection with the Scarab strengthens, allowing him to overcome Carapax.

In a twist, Carapax's tragic past is unveiled, showing he was manipulated into serving Victoria. He self-destructs, killing both himself and Victoria. Jaime accepts his destiny as Blue Beetle, and he and Jennifer vow to protect their city.

Two post-credits scenes provide insight into the future. Uncle Rudy's admiration for the Mexican hero El Chapulín Colorado honors Mexican culture. The second scene unveils Ted Kord's survival, setting up potential sequels.

Jaime's story underscores the strength of family bonds. His love for his family fuels his heroism and determination. The film implies that while it might not connect to larger DC Universe events, Blue Beetle solidifies Jaime Reyes as a prominent character within the DC Universe.