Episode 4 of "Percy Jackson and the Olympians" begins with a glimpse into the past, where Sally, Percy's loving mother, takes her son to a serene pool to introduce him to the art of swimming. Despite Percy's initial reluctance, Sally, deeply concerned about his future safety, urges him to embrace the challenge. She gently encourages him, and Percy, in turn, asks his mother to take a deep breath, echoing her own words of comfort whenever he feels anxious.
In the present timeline, the trio embarks on a perilous journey on a train, heading towards the underworld to fulfill their destiny. Percy and Annabeth engage in a meaningful conversation while Grover sleeps peacefully, unaware of the dangers that await them.
Annabeth reveals to Percy the unusual circumstances of her birth, explaining that Athena's thoughts gave birth to her and bestowed her upon her biological father. Initially, she enjoyed a fair treatment, but things took a turn when her father found a new partner and had his own children with her. Suddenly, Annabeth became a burden to her stepmother, and as a result, she was forced to leave her home at a tender age, eventually finding solace at Camp Half-Blood.
The following morning, the trio faces yet another obstacle as they are hunted by the fearsome mother of monsters, Echidna, and her pet monster, Chimera. Despite their valiant efforts, the relentless pursuers refuse to give up, even after the trio disembarks from the train.
As they arrive in St. Louis, Annabeth guides Grover and Percy to the sanctuary of the Athena temple, seeking refuge from their relentless pursuers. Grover's anger flares up when he witnesses the cruelty towards animals, feeling a deep sense of personal responsibility as a Satyr himself. The trio braces themselves for the next chapter of their adventure, knowing that the path ahead is fraught with danger and uncertainty.
Not long after, Echidna and Chimaera received Athena's blessing and made their way into the temple. It transpired that Athena was displeased with Annabeth's decision to send Medusa's head to Mount Olympus. As a punishment, she allowed Echidna and Chimera to enter the sacred grounds.
The trio ventured towards the summit of the temple, and soon, Percy found himself in a perilous situation. He insisted that Annabeth and Grover descend into the underworld while he faced Echidna and Chimera alone. However, due to the injuries he sustained during the train attack, Percy was unable to fight valiantly.
Without mercy, Echidna and Chimaera shoved him off the precipice of the temple, sending him tumbling down from a towering height. Yet, in a moment of divine intervention, a wave from Poseidon swooped in and transported Percy to the Mississippi River.
As he struggled to stay afloat, a nymph appeared and gently instructed him to breathe. Thanks to Poseidon's blessing, Percy found himself able to breathe underwater. The episode drew to a close with the nymph reassuring Percy that his father was proud of him and was watching over him protectively.
