There Will Be Blood starts with oil and ends in — you guessed it — blood, but at its core is a story of corruption. Based so loosely on Upton Sinclair’s novel Oil! that writer-director Paul Thomas Anderson admits to using no more than the first hundred and fifty pages, it mostly eschews Sinclair’s hits at capitalism, political scandal, and charismatic young preachers in favor of a deep character study. Untrustworthy evangelicals and the corrupting influence of money still have their place, but at its core, There Will Be Blood chooses to focus on one man’s path into darkness.

Nowhere is that path more obvious than when we follow Daniel’s relationship with his son, H.W., adopted when his birth father dies in one of the many violent accidents that accompany the early oil boom.

Daniel’s full motives for adopting H.W. are unclear, but by the time the boy is old enough to speak, he has become Daniel’s quiet, charming partner in crime, a friendly face to impress and disarm the yokels and reinforce Daniel’s image as a family man. Daniel may consider the boy a tool, but he also treats him with respect, even when no one is there to witness their interactions. But over the course of the movie, this relationship — perhaps the only healthy, caring relationship Daniel ever had — frays and breaks.

They take the first step down the path to alienation in another accident, one that costs H.W. his hearing. Daniel runs to the boy in a panic, carrying him to safety, but then abandons the terrified child, asking one of his men to hold H.W. down as he runs back to the oil fields. From that moment of betrayal, the bonds between father and son begin to weaken. Eventually, when caught between his adopted child and the man he thinks is his long-lost brother, Daniel opts for the illusion of a blood tie rather than the authentic love he had always received from H.W. He tricks the boy and puts him on a train bound for San Francisco.

Sent away from his father, H.W. becomes a stronger and better man for it, rising to become someone with greater honesty and integrity as his father falls lower and lower. When we see H.W. as a grown man, he’s eager to make his own way in the world, with or without his father’s approval. Once, Daniel had cared enough to provide H.W. with an interpreter, and send him to a school for the deaf (no guarantee in the early twentieth century). In their final scenes together, Daniel rejects the ASL he had once supported, dismissing it as “hand-flapping.” He accuses H.W. of “building new hate for me, piece by piece,” though the viewer knows that alienation and separation from H.W. was Daniel’s choice. Daniel continues to yell as H.W. walks away, even though he and the viewer are well aware that H.W. can’t hear a word he says.

Alienation and loss of family is also a throughline in the life of Daniel’s foil and adversary, Eli Sunday. Eli’s fall is less central to There Will Be Blood, but the movie wouldn’t succeed half as well without it. We see Eli’s brother, Paul, leaving the family before we even meet the Sundays. When we do, Eli is already a successful child preacher, and the only person in their small community who successfully sees through Daniel’s family-man façade. It’s not enough to turn the tide against Daniel, and the frustration clearly eats away at Eli. He uses his power to intimidate his own family (though it’s not enough to spare his sister from violence; it takes H.W., through Daniel, to put an end to her beatings), but his siblings are both driven away by the movie’s end. Eli and Daniel know one another better than anyone else in the film; they each know exactly where to hurt the other, and one of the most disturbing moments in There Will Be Blood is when Eli forces Daniel to confess that he sent away his own child. Daniel’s pride is easy enough to bruise, but the truth is the sharpest and cruelest weapon. But Eli’s triumph is temporary; the world takes its toll soon enough.

The towering final scene underlines how much both men have lost. Eli attempts to squeeze money out of Daniel, using the last holdout in the oil field as leverage. But Eli has miscalculated; not only does he not understand how oil drilling works, he tries to persuade Daniel to work with him by reminding him that, thanks to Mary’s marriage to H.W., “we’re family.” Daniel, still smarting from the loss of H.W., lets loose his rage. He torments Eli with his own betrayals, telling an exaggerated story about Paul Sunday’s success and glorying in Eli’s failures. But even that victory isn’t enough; it proves as hollow as the near-empty mansion Daniel inhabits. All that Daniel has left to offer the world is destruction. With the last shreds of his morality frayed beyond repair, Daniel Plainview picks up a bowling pin and finishes his work.

(I sometimes catch myself wondering what H.W. would do in the wake of Daniel’s final act. Would reporters ask him questions? Would he pay for his father’s defense? Or would he slip quietly away to Mexico with Mary, as he’d planned, and leave the final remnants of his past behind?)

Fun fact #1: the California School for the Deaf was founded in San Francisco, but by the events of There Will Be Blood, it had moved to Berkeley. The school continues to this day, providing bilingual Deaf education. It is, of course, a pure guess as to whether or not Daniel meant to do the best he could by H.W. by choosing a school in San Francisco that taught ASL, but “oral only” education was common through the 1950s and still has holdouts today. Russell Harvard, who plays the adult H.W., researched vintage ASL for his scene, and if ever there was proof that someone belonged on-set with Paul Thomas Anderson and Daniel Day-Lewis, that might be it.

Fun fact #2: Sunday appears in both Oil! and There Will Be Blood, and was loosely based on Aimee Semple McPherson, founder of the Foursquare Church and a controversial figure in her own right.