Is there any way to recover access to an account that is vital to a store/home/family after the sudden death of the account holder?
The Agilebits company has no way to unlock a customer's vault. The encryption is very strong, and without the account holder's master password, the data are quite secure from access: that's the whole point of 1Password. Now if the account holder has written down the master password and saved it in a safe deposit box or in some insecure location like a folder in the desk, if you find it you can get in. It is unlikely that a 1Password user would set an easy-to-guess master password, so trying to guess the master password probably won't succeed.
I believe that the 1Password Family product and the 1Password Team product do have the possibility for the "main" account holder to recover passwords for the secondary account holders, but again that depends on knowing the main account holder's master password, and the Agilebits company does not know this password.
I'm going to move your question to our Lounge category, as it's a topic that affects all of the platforms! What @bkh said is correct. On the standalone versions of 1Password, you can't open (decrypt) a vault unless you have the Master Password, and we don't have a way to change it or reset it. That's exactly one of the big points of 1Password's strength. One thing to keep in mind is that you can try as many passwords as you need, and it will never be locked down. If you think you remember something that will help you guess it you can always try.
In the other hand with 1Password Families or Teams you do have the option of "account recovery". This can only be done by someone who has Admin privileges, but you can't recover your own account so it's important to have everything set up properly. You can read more about how this works here: https://support.1password.com/teams-admin-recovery/#have-a-recovery-plan.
Please let us know if you have any other questions or there's anything else that you'd like to know about 1Password