The children begin to unravel the mystery around the missing red diamond; Max keeps a secret from his siblings. 
- Stony Blyden as Max Hunter
- MaeMae Renfrow as Tess Hunter
- Daan Creyghton as Sal Hunter
- Thomas Jansen as Daniel Hunter
- Kyra Smith as Anika Hunter
- Yootha Wong-Loi-Sing as Simone
- Barnaby Savage as Tim
- Ronald Top as Erik Hunter
- Tooske Ragas as Kate Hunter
- Rob Andrist Plourde as The Museum Facilitator
- Erik and Kate thought that the Red Diamond doesn't exist until this episode.
- Some parts of the episode were shot in Nederlands Scheepvaartmuseum (National Maritime Museum) in Amsterdam.
| To view the The Red Diamond gallery, click here.
|Hunter Street Episodes|
|The New Hunter • Saganash • The Secret Room • Principal • Rinus • The Key • The Blue Diamond • MGP • Aunt Hedwig & Uncle Eugene • Contact • The Relatives • The Red Diamond • Cassandra's Map • Anika's Birthday • The Maze • Undercover • Sophie • Bruhl • Almost Back • The Deed|
|The Package • The Arrest • Max • Evie • The Museum • The New Friend • The Family Tree • Payback • The Plan • The Reverse Heist • The Mole • The Green Mask • Hacker Hideout • The Super Secret Room • The Crown • Hide and Seek • The Houseboat • Spy • The Ritual • Hunters Forever|