On Beauty and the Beast Season 3 Episode 12, Cat and Vincent are ready to take Liam down once and for all and this time they are bringing in the big guns. Vincent comes up with the idea to erase Liam's memories like his were erased and Cat enlists the help of her father, Robert. Robert tries to convince Cat that erasing memories isn't easy and that it takes time, but Cat explains that she doesn't have time to waste and they need to erase Liam's memories now. Robert tries to convince Cat to take him out of prison on a furlough, but she declines his help and instead wants just the formula.
At the hospital were Vincent works Helen Ellingsworth is brought in because she is dying from possibly poisoning. Vincent tries to explain to her Liam is the one to blame for what she's going through, but she doesn't want to believe him. Liam shows up after Vincent leaves Helen's room and injects Helen with a concoction which immediately kills her and causes Vincent to be put on probation by the hospital. This convinces Cat they need to get Robert's help in taking down Liam and Vincent breaks him out of prison.
At JT's apartment, Robert is working on the formula while Vincent and Cat go to track down Liam. They are able to subdue him and bring him back to the apartment where Robert slowly administers the formula and tries to erase Liam's memories. Liam is able to fight the formula and Robert makes everyone else leave the apartment so they won't get hurt. Liam vows to take down both Cat and Vincent and kills Robert.
In the end, Cat mourns the loss of her father and realizes they are going to have to go to great lengths to get Liam out of their lives.
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