Birha is an elderly mathematician who is an expert on alien technology. She lives alone on an alien planet, spending her days determining the probabilities distributions of the various universes present on the cosmic tree, known as the kalpa-vriksh. Birha was the one to discover the existence of the kalpa-vriksh. When she was younger, she went on a rescue mission to recover a pilot who had accidentally flown into an alien ruin. The alien inhabitants were presumed dead, but when she arrives in the dome, she learned this is not the case. The aliens had built an actualizer, a probability machine that acts as a liminal space between universes. With the actualizer, people can travel between dimensions, but because of the discrepancies of time and space, they don’t always come back the same age or with the same identity. Eventually, Birha loses her friends, colleagues, and students to the lure of a new world until she is left with only the strangers in her town.

Birha’s monotony is broken by one thing: the hope that Rudrak will return to visit her before she dies. Rudrak is a traveler from a universe very similar to Birha’s. While exploring the heart of a star, he became stuck in a time loop which repeatedly sends him across the barrier between their two universes. Birha always sends him back to his home universe through the actualizer, but he nonetheless returns sporadically with no apparent memory of his last visit. Each time he is a little different from the last, a little older and often wearing different clothes. Birha loves him in spite of the impossibility of their being together. Besides the inconvenience of the time loop, Rudrak is also still in love with Ubbiri, another resident of his home universe. Each time he arrives, he is looking for her. And each time, Birha must break the news that she has died. Before Rudrak arrives for the first time, Birha meets Ubbiri in the chamber of the actualizer. Ubbiri reveals that her partner had disappeared and that she had followed him into the star. Unlike Rudrak, however, Ubbiri does not keep her age when she arrives in Birha’s universe. Instead, she becomes an old woman and dies soon after revealing the truth to Birha. Now an old woman herself, Birha wonders if she will see Rudrak before she dies. She feels death approaching quickly and cannot find a suitable probability to predict when he might arrive again. She contemplates walking into the forest and allowing the human-eating plants to take her. But a few days after her thoughts turn to despair, there is a knock at the door. Rudrak has arrived for one final visit. He steps into her home, looks around, and asks her with a look of wonder if he’d been there before.