THE Big Bang Theory fans think they've solved the emotional truth behind Howard’s letter from his dad.
The hit CBS sitcom may have came to an end in May last year after 12 seasons, but it hasn't stopped fans from pouring over the episodes for things they might have missed first time around.
And in a season six episode, fans are convinced they have solved what was in a letter to Howard (Simon Helberg) from his estranged father.
Neither of Howard's parents appear in the series, as viewers only ever hear his mother's voice off-camera in scenes at his home.
In the episode The Closet Reconfiguration, Bernadette and Sheldon help Howard sort out his messy wardrobe, before Sheldon (Jim Parsons) finds a letter from Howard's dad, Sam.
Sam abandoned Howard and his mum when he was 11, so he decides to burn the letter without reading it.
However, Sheldon manages to read a few passages before he does so, and later decides to share with the group what he read in order to help Howard calm his nerves.
Each of Howard's friends then share what they think the letter contained, with only one account being true, with Raj saying it was a 1 18th birthday card and Bernadette revealing it contained a photo of Howard as a child.
Sheldon delivers a curveball theory that the letter had a map leading to hidden treasure inside like in the classic 1980s film The Goonies.
But fans believe Amy (Mayim Bialik) is the closest to the real contents of the letter, thanks to how she delivers her theory.
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Writing on Reddit, one viewer said: "I read somewhere that it was Amy because she’s the only one who was seated that stood up when it was her turn.”
Others pointed out how Amy was close to tears as she gave her account of the letter, saying: "You didn’t know it, but your father was in the auditorium at your high school graduation.
"And he cried because he was so proud of you.”
The Big Bang Theory is available to stream on Netflix.