Howard, who was a successful and happy person, lost his 6 year-old-daughter because of a rare form of cancer.
After the death of his daughter, Howard went into a state of denial where his mind became absent most of the time and kept playing with the domino parts his daughter used to play with over and over.
After the incident, Howard sent a letter to Madeline, his wife, and told her that it's better that they become strangers again. Throughout the movie Howard pretends that he doesn't know Madeline and she plays along with him.
Howard, unable to accept the death of his daughter, started to write letters to love, death and time.
Howard's partners want to save the company and secure their financial future by selling it. They decided to create a case and prove that Howard is mentally unstable so that they can proceed with the sale.
Howard's partners hired 3 actors to play the roles of love, death and time in order to prove that Howard is out of his mind. their plan was to let him talk to those actors then remove the actors from the videos using photo-editing programs.
The actors turned out to be non-humans and they were actually death, love and time disguised as humans.
Bridgette, who plays the role of death, told Madeline right before she lost her daughter that she must always look for Collateral Beauty during tough moments.
With the help of love, death and time, Howard came to accept what happened. He met his wife and mother of his daughter, Madeline, and talked about their past days. Howard finally accepted reality.
Finally, the couple, and especially Howard, managed to see the Collateral Beauty beauty which are the meaningful moments behind a bad event.
In the final scene, death ,love and time watched Howard and Madeline from a distance as they accepted reality and went on with their lives.