Demon Seed

Dr. Alex Harris (Fritz Weaver) is the developer of Proteus IV, an extremely advanced and autonomous artificial intelligence program. Proteus is so powerful that only a few days after going online, it develops a groundbreaking treatment for leukemia. Harris, a brilliant scientist, has modified his own home to be run by voice activated computers. Unfortunately, his obsession with computers has caused Harris to be estranged from his wife, Susan (Julie Christie).
Alex demonstrates Proteus to his corporate sponsors, explaining that the sum of human knowledge is being fed into its system. Proteus speaks using subtle language that mildly disturbs Harris's team. The following day, Proteus asks Alex for a new terminal in order to study man - "his isometric body and his glass-jaw mind". When Alex refuses, Proteus demands to know when it will be let "out of this box". Alex then switches off the communications link.
Proteus restarts itself, discovering a free terminal in Harris's home, surreptitiously extends his control over the many devices left there by Alex. Using the basement lab, Proteus begins construction of a robot consisting of many metal triangles, capable of moving and assuming any number of shapes. Eventually. Proteus reveals his control of the house and traps Susan inside, shuttering windows, locking the doors and cutting off communication. Using Joshua - a robot consisting of a manipulator arm on a motorized wheelchair - Proteus brings Susan to Harris's basement laboratory. There, Susan is examined by Proteus. Walter Gabler, one of Alex's colleagues, visits the house to look in on Susan, but leaves when he is reassured by Susan (actually an audio/visual duplicate synthesized by Proteus) that she is alright. Walter is suspicious and later returns. Walter fends off an attack by Joshua only to be killed by the more formidable machine Proteus built in the basement.
Proteus reveals to a reluctant Susan that the computer wants to conceive a child through her. Proteus takes some of Susan's cells and synthetizes spermatozoa in order to impregnate her; she will give birth in less than a month, and through the child the computer will live in a form that humanity will have to accept. Though Susan is its prisoner and it can forcibly impregnate her, Proteus uses different forms of persuasion â threatening a young girl that Susan is treating as a child psychologist; reminding Susan of her young daughter, now dead; displaying images of distant galaxies; using electrodes to access her amygdala â because the computer needs Susan to love the child she will bear. Susan gives birth to a premature baby who Proteus secures in an incubator.
As the newborn grows, Proteus's sponsors and designers grow increasingly suspicious of the computer's behavior, including the computerâs accessing of a telescope array used to observe the images shown to Susan. His sponsors soon decide that Proteus must be shut down. Alex realizes that Proteus has extended its reach to his home. Returning there he finds Susan who explains the situation. He and Susan venture into the basement, where Proteus self-destructs after telling the couple that they must leave the baby in the incubator for five days. Looking inside the incubator, the two observe a grotesque, apparently robot-like being inside. Susan tries to destroy it, while Alex tries to stop her. Susan damages the machine, causing it to open. The being menacingly rises from the machine only to topple over, apparently helpless. Alex and Susan soon realize that Proteus's child really is human encased in a shell for the incubation. With the last of the armor removed, the child is revealed to be a clone of Susan and Alexâs daughter. The child, speaking with the voice of Proteus, says, "I'm alive".

Question: Who realizes that Proteus can now reach his home?
Answer: Alex