Contemporary live debuggers do not display the complete call stack history for concurrent threads. Hence, developers have less information at their disposal when debugging concurrent threads than when debugging a single threaded, sequential program. We solve the problem of incomplete thread history by creating a debugger that operates on a virtual call stack comprised of multiple threads. With live debuggers displaying at least the equivalent information for both single threaded, sequential programs and concurrent threads, developers can focus on the hard parts of concurrency issues.