The Observers are indeed in effect eternal - I first called the Observer Eternal Bald when he was first introduced in episode 1.4 last year, as a way of pointing out that science fiction often seems to have an Observer who is bald and around for a long time - but last night we learn that the Observers have been present at an odd series of notable events in human history, ranging from the Boston Massacre in 1770 to the beheading of Marie Antoinette in 1793. I wondered why Fringe didn't show us an EBO at the death of Socrates or the Crucifixion, but maybe there's some reason for the presence of Observers at just certain important events that we don't yet know.
The Eternal Bald Observers are here only to observe, but they've interfered with our affairs twice. Last night brought us the more or less complete story of one of the interventions. An Observer at the San Francisco earthquake of 1989 is taken by the bravery of a young girl whose parents die. He thereafter has kept a watchful eye on her, and intervenes again, in our present, to prevent her from getting on a plane in Boston which will crash in Rome. The other Eternal Bald Observers - there's a table of them, including the EBO we met last year, who is not the same one who has been watching the girl - don't want any intervention, and hire a human assassin to clean up this problem, i.e., kill the girl.
But the EBO keeping watch on the girl can't allow this to happen. He's grown to love her, in an avuncular, protective way. Walter tells him he (the EBO) must do something to make the girl - now in her 20s - significant enough to make the board of EBOs want to keep her alive. He allows the human assassin to kill him, while orchestrating the woman's escape. His death in protection of the woman makes the woman special enough to warrant the EBOs' continuing protection of her - he's the first EBO to die on behalf of a human. Apparently his love of her, which impelled him to protect her, wasn't in itself enough - which is sad, but those EBOs are a tough bunch to convince.
The other time the EBOs intervened in our affairs is when they saved Walter and Peter. The older EBO leader apparently alludes to this when he tells his colleagues that this intervention was warranted because it corrected something which wasn't supposed to happen. The EBO we met last year was the point bald man on this, and he presumably also had a role in Walter's taking of Peter from the alternate reality after Peter died as a boy in our reality.
Peter still does not know his real identity, and his story is the most compelling in Fringe, humanizing Walter as a father willing to breach alternate realities to "keep" his son, and putting the two on collision course as Peter learns more about the Observers and Walter strives to keep Peter in the dark about his origins. The unanswered questions that loom - including what happened to the Walter in the reality from which our Peter was taken - promise some outstanding Fringe in months and more to come.
10-min podcast review of Fringe
See also Top Notch Return of Fringe Second Season ... Fringe 2.2 and The Mole People ... Fringe 2.3 and the Human Body as Bomb ... Fringe 2.4 Unfolds and Takes Wing ... Fringe 2.5: Peter in Alternate Reality and Wi-Fi for the Mind ... A Different Stripe of Fringe in 2.6 ... The Kid Who Changed Minds in Fringe 2.7
See also reviews of Season One Fringe Begins ... Fringe 2 and 3: The Anthology Tightrope ... 4: The Eternal Bald Observer ... 7: A Bullet Can Scramble a Dead Brain's Transmission ... 8. Heroic Walter and Apple Through Steel ... 9. Razor-Tipped Butterflies of the Mind ... 10. Shattered Pieces Come Together Through Space and Times ... 11. A Traitor, a Crimimal, and a Lunatic ... 12, 13, 14: Fringe and Teleportation ... 15: Fringe is Back with Feral Child, Pheromones, and Bald Men ... 17. Fringe in New York, with Oliva as Her Suspect ... 18. Heroes and Villains across Fringe ... Stephen King, Arthur C. Clarke, and Star Trek in Penultimate Fringe ... Fringe Alternate Reality Finale: Science Fiction At Its Best