Dreams involving infidelity can be quite distressing and often reflect our own insecurities or fears in a relationship. In your dream, the setting of a cabin that resembles your childhood home suggests a connection to your past and possibly unresolved feelings or memories from that time. The presence of your deceased sister may indicate a longing for support or guidance in dealing with your current emotional struggles.

Seeing your partner sneaking away can symbolize feelings of betrayal or mistrust, which might stem from your subconscious concerns about the stability of your relationship. The fact that you didn't confront him but observed his actions could indicate a feeling of powerlessness or uncertainty in addressing these issues directly.

Being unable to leave the cabin might represent feelings of entrapment or being stuck in your current situation, whether it's related to your relationship or emotional state. This could suggest a need to confront your feelings and communicate openly with your partner.

To gain clarity, consider reflecting on your current relationship dynamics and whether there are any underlying issues that need to be addressed. Open communication with your partner may help alleviate any fears or doubts you have. Additionally, seeking support from friends or loved ones, or even professional help, might be beneficial in processing these emotions.