Who collects the life insurance if the policy holder and beneficiary have died?

If the beneficiary of a policy has died, the estate of the beneficiary can still collect the insurance payment, assuming that the beneficiary does have an heir or heirs of some kind (as most people do). Note that this is a fairly unusual situation, because normally when a beneficiary dies, a new beneficiary is named. There is no reason to allow the policy to have no living beneficiary, unless the insured and the beneficiary happen to die at about the same time, and there is no time to name a new beneficiary.