Agatha Christie: And Then There Were None [cheats]
Once the safe has been opened, inside is a small drawer with slots with the letters A, E, E, E, H, L, R, S, T, U, V and W. Notice the poster above the radio just outside the safe. You will find the answer there in a song that Patrick sings. The answer to open this second hidden door is: Rule the Waves.
Miss Brent alive and dead at the same time
The game may glitch to where Miss Brent knitting downstairs on the patio alive, but is also dead in bed at the exact same time. This happens because she must first complete the part of your escape plan that you have given her, which is to sew the two sheets together. For her to finish this you must give her: sheets (found in the upstairs closet) sewing needles (found in the Rogers' room) and finally fishing line (found behind the thorn bushes). To get past these thorns, find the fermented apples near the bee hives. Using the cheese cloth, place them in the juicer in the kitchen. You will need a piece of the submarine hidden through the "Rule the Waves" door before you can do this. Make sure that you explore the rooms beyond the safe very carefully or you will miss the sub. After you have the apple cider, take it to the thorn bush and use it there. Grab the fishing line and give it to Miss Brent. Walk away for a few minutes and return. The sheets are done and you can combine the four things you need: the tri-pod for the telescope, the sheets, the leather goat harness and the fishing net to get your parachute.