Black Chamber ep. 000f02 - The Red Triangle cipher

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The second of the "ciphers in fiction" videos. This one for Arthur Morrison's The Red Triangle. Can you solve this without help?

Lever Key cipher:

9, 8, 14, 4, 20, 18, 5, 9; 15, 19, 20, 0, 3, 9, 8, 5; 3, 23, 0, 0, 5, 13, 14, 19; 19, 20, 0, 0, 0, 0, 6, 1; 5, 20, 0, 0, 0, 0, 3, 22; 1, 15, 0, 0, 0, 0, 18, 5; 1, 8, 20, 11, 18, 9, 5, 20; 12, 5, 23, 14, 14, 1, 1, 20.

Channel Marsh cipher:

23, 19, 15, 1, 9, 14, 9, 2; 20, 8, 1, 20, 14, 14, 20, 8; 14, 5, 12, 4, 9, 7, 5, 14; 3, 8, 18, 23, 0, 14, 1, 8; 22, 9, 6, 1, 18, 3, 5, 1; 19, 14, 15, 21, 9, 0, 20, 12; 18, 12, 21, 1, 6, 23, 20, 12; 9, 18, 15, 5, 18, 13, 12, 20