NCIS season 13 returns with its fall finale episode on 15 December, where fans will learn about Dr Donald Mallard aka Ducky's childhood and his relationship with his brother. Episode 11 is titled Spinning Wheel, which airs this Tuesday at 9pm EST on the CBS Network.

The official synopsis reads as follows:

After Ducky is attacked by a man claiming to have information about his half-brother who died decades ago, the NCIS team searches for the perpetrator, as Ducky recalls the final emotional days he had with his sibling. Also, with the holidays approaching, Bishop and Jake (Jamie Bamber) discuss the future of their relationship.

Click here to watch the episode live via CBS All Access. You can also watch the episode online by clicking here (only in the US).

Warning: Potential spoilers ahead.

Actor Adam Campbell has been cast to play a younger version of Ducky. The NCIS officer will recall the emotional final days with his younger brother after he is attacked by a man claiming to have information about his family. Fans will see a lot of flashback of a young Ducky conversing with his older brother.

In the latest promo of the episode, Leroy Jethro Gibbs asks Ducky, "Is there a reason you never told me you had a brother?" To which Ducky reveals, "He passed away." However, Abby has some proof that he is still alive.

Elsewhere in the episode, Eleanor "Ellie" Bishop (Emily Wickersham) will deal with her marital problems with Jake (Jamie Bamber) in the episode. The couple will finally have a talk and she learns that Jake was unfaithful in their marriage.