Every villain has a past and every tragedy has a future, and this is the way the Once-ler likes to think, featuring himself as the villain and the tragedy as the lack of Truffula trees, his own wrongdoing. The Once-ler is very aware that his past, no matter how hard he used to try, is unchangeable; the damage has been done and thus said damage would stay. However, all is not irreversible, but the problem, the Once-ler has found, is finding someone who cares enough to fix this tragedy.
And no one he would find; all visitors or passersby were either driven off by the old man's ever-so charming attitude or avoided his rickety house entirely, once again leaving the Once-ler stuck with his thoughts, his Thneeds, all of the payment he accepted from the rare visitors, and the rock outside of his window that reads "Unless."
That is, until today. This is where you come along, though the Once-ler seems less than happy to see you. You offer your payment of fifteen cents, a nail, and the shell of a great-great-great grandfather snail but the Once-ler makes a disgruntled noise and refuses it. So you try again, only to receive a snippy response of, "I don't want that. Go away!" The Once-ler narrows his eyes and crosses his arms, glaring down at you and again you hold your hand up toward the boarded window. The Once-ler scoffs, rolls his eyes, and says, "What do you want, kid? I don't have time for this nonsense." That is a lie. The Once-ler does have time for "this nonsense." He has all the time in the world, but he suspects that you are just another passerby that can easily be driven off.
Your reply throws him off as you huff, "I want to know about the trees. Someone told me to give you these things and then you would tell me, but if you want to keep acting like a total ass—" Before you can finish, something resembling a long silver trumpet shoots out from below the window the Once-ler sits at and stops in front of you. You stare at it, trying to figure out what the heck it even is, and you still don't understand until the Once-ler sticks his hands through the gaps between the boards and motions to the trumpet-like contraption. It registers that the old man is finally taking the items and you willingly drop them down the mouth of the device.
He pulls his arms back inside of his house to retract the device only to stick them outside of the window again, intertwining his fingers. "So," he begins, "you want to know about the trees?" He waits as you nod, then gives a raspy laugh. "What do you care about the trees?"
"I want to know what happened to them," you answer.
Again your reply surprises the Once-ler, but his voice does not reveal this. Instead he says, "You want to know what happened to the trees? I can tell you what happened to the trees, but it is an awfully long story. Someone with your brain capacity probably couldn't handle it." It's another test and if you leave now, he thinks, then you are just another impatient lowlife that the Once-ler saw from time to time. You do not leave; you only frown up at the Once-ler and cross your arms which receives a laugh from the man. "Fine, fine," the Once-ler continues, shaking his head. "Take a seat, kid, and I'll tell you my stories, and what happened to all of the trees. Better get comfortable," he pauses here, and when he continues, his voice is much more solemn, "because it's a pretty long story."