What is the fastest way to order an unordered list of elements by predecessor (or parent) element index using LINQ?

Each element has a unique ID and the ID of that element's predecessor (or parent) element, from which a linked list can be built to represent an ordered state.

Example

ID      | Predecessor's ID
--------|--------------------
20      | 81
81      | NULL
65      | 12
12      | 20
120     | 65

The sorted order is {81, 20, 12, 65, 120}. An (ordered) linked list can easily be assembled iteratively from these elements, but can it be done in fewer LINQ statements?

Edit: I should have specified that IDs are not necessarily sequential. I chose 1 to 5 for simplicity. See updated element indices which are random.