Two secrets has been exposed in this episode, first it was Lizzie who was feeding the Walkers with rats back at the prison. She was also the one who dissected a rat and nailed it to a board.
The episode started with good fortune as Mika and Carol found a house with a lot of water and a pecan grove. They were thinking they can live in that place for good and not head for the Terminus. But things got ugly fast, Carol saw Lizzie playing with a walker by letting it chase her around. And after that when Carol and Tyreese were out in the forest looking for God knows what, they saw Lizzie with a bloodied hands, she stabbed her sister to death thinking that it's all right and she'll come back.
"Don't worry, she'll come back. I didn't hurt her brain," Lizzie told Carol. Both Tyrese and Carol look terrified at what she'll do with baby Judith.
Carol told Lizzie "Just look at the flowers, Lizzie. Look at the flowers," then she shot Lizzie, you just can't save a broken child.
The second secret exposed in this episode, Carol admitted to Tyrese that she was the one who killed Karen (Tyrese sick girlfriend back at the prison). Carol expect Tyrese to kill her passing a gun to him, but Tyrese forgave her. Carol lost so much already, losing her daughter way back, this time losing two of her students which she treated as her own daughters.