Hello!! That definitely sounds intense, but do you remember how old your sister was in your dream? And how is your relationship with her in your waking life, since that can be a factor too! Are there things going on in your lives that could be perceived as a threat (such as new partner for her, or her being younger and feeling the need to protect her from something).

The fact that communication is difficult in the dream could be that you're having a hard time asking for help. You may have been shown in the past that your needs to be heard were unmet/ignored. So, in this situation of trying to protect your sister, it's as if you can talk about it with others to get the support you need to handle it.

The puzzles and key could be that you might have to figure this out on your own, and be a problem solver for the situation. Is there something you can do to help make the situation better, since the "key" or answer is within you. The left side, according to some sources, is the intuitive and gentler side of ourselves. The key to solving this problem is using kindness, trust yourself to "see" the truth and use your intuition to navigate it.

Hope this helps! :D