Bonnie finally learned why she's been feeling Enzo's presence since his death on The Vampire Diaries. Unfortunately, she needed to connect with Cade to do so. In "The Lies Will Catch Up To You," Bonnie reached out to Cade after feeling a strong connection to him. When she confronted Cade about their connection, he told her exactly what was going on with her: she created an alternate dimension, just like he did when he created Hell all those years ago. But, why did Bonnie create an alternate dimension on The Vampire Diaries? Cade has the answers, but he's not giving them for free.
Enzo's death and the immense, emotional trauma Bonnie felt watching him die, caused her to create "a powerful psychic blast" that created an entire dimension for Enzo's soul to enter after death. According to Cade, Enzo's death triggered her in a way so powerful, she created an entire dimension for Enzo. This dimension, it seems, is tied to her and her alone, which might explain why Cade is so eager to help her connect to it. See, he's not just helping Bonnie out of the kindness of his heart. He wants Enzo's soul because, as a vampire, he believes that Enzo deserves an eternity of fire and torture, not an afterlife in Bonnie and Enzo's cabin.
Bonnie is able to protect Enzo from Cade, successfully hiding him in her dimension for now. At the end of the episode, she was even able to summon him back to her, though not entirely. Though she can touch him, kiss him, and talk to him, Enzo isn't really back. Like Kai, he seems to be in an in-between state of being — not entirely dead, but certainly not alive for good either.
Bonnie shouldn't get used to having Enzo back, especially with Cade after him. It's only a matter of time before Enzo's death catches up to them. And who knows what Cade will want then.