Following the death of his brother, hunter Sam Winchester became determined to get revenge upon Lilith. After returning from Hell, Ruby attempted to teach Sam to use his psychic powers to exorcise demons with no luck for about a month.
Around a month after Dean's death, Lilith decided to set an ambush for Sam. She caused demonic omens that indicated her presence in town, but in reality left two assassins to kill Sam. To this end, the assassins set up in a house where they forced a little girl to sit in front of a table of sweets, making it appear as if she was possessed by Lilith. As Lilith planned, Sam spotted the signs and chose to go after her on what Ruby realized was a suicide mission. Despite Ruby's protests about the suicidal nature of the mission and Sam not being ready, he went anyway.
Approaching the house, Sam spotted what he believed to be Lilith at the table through the front window. Entering cautiously, Sam makes his way towards the little girl who tearfully turns around and tells him that she wants to go home.
Before Sam can react, he is grabbed from behind, disarmed of the demon-killing knife and pinned to the wall by two demon assassins. One tells Sam that "Lilith sends regrets. She couldn't make it." As the demons forcefully pin Sam to the wall, Ruby enters, grabs the knife and slits the throat of one of the demons, killing him and shoves the other off of Sam.
Telling Sam to "take the girl and run", Ruby fights the remaining demon who proves to be stronger than her and is unharmed by Ruby's blows. Nearly breaking Ruby's arm, the demon disarms her and pins Ruby against the wall. The demon taunts Ruby about how much trouble she is in and what they will do to her once they get Ruby back in Hell. However, before the demon can harm Ruby further, Sam uses his psychic abilities to exorcise the demon from his vessel and back to Hell. The exorcism gives Sam a nosebleed but leaves him jubilant as it is the first time he has ever successfully exorcised a demon with his powers.
Five months after the ambush, Sam told the resurrected Dean the story as part of why he trusts Ruby. Sam notes that Ruby came back for him to save Sam during the ambush and finally got through to him with her words and actions as a result due to their similarities to what Dean would've told him.