Extensive summary of the plot

Serial experiments lain from my understanding is about the protaginist lain learing about the wired (the internet) and how to connect with others using the wired as an advanced medium of communication.

Lain initally has no experience at all using the wired unti she hears a rumor from one of her friends that a girl named Yomida Chisa commited suicide, yet has been sending email to all her classmates on the wired from beyond the grave. Curious about how this is possible, and why Chisa commited suicide Lain boots up her old childhood navi (computer) and checks her mail, and to her surprise, she has mail from Chisa. They have a short conversation where lain repeatedly asks Chisa why did she die? But Chisa ignores this question, and simply tells lain "God is here" (referring to within the wired) Creepy!

Eventually lains interest in the wired requires a more powerful machine so she decides to ask her father Yasuo for a new navi, which to her surprise he agrees and buys her a top of the line navi.

During her online adventures lain unkowingly comes into contact with a group of hackers called "the knights" which take great interest in her, as lain (who thinks she is simply an awkward schoolgirl) is actually the creation of Masami Eri a deceased man who worked for Tachibana industries a japanese tech company who developed the wired. The knights (formerly known as the knights templar) worship Masami Eri as a god within the wired and do his bidding, meddling with the real world in various ways thorugh their hacking and mind altering drugs they distribute called Accela.

Lain is invited by her friend Arisu to come to a nightclub called Cyberia