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The power of science lies in its ability to infer and predict the existence of objects from which no direct information can be obtained experimentally or observationally. A well known example is to ascertain the existence of black holes of various masses in different parts of the universe from indirect evidence, such as X-ray emissions. In the field of complex networks, the problem of detecting hidden nodes can be stated, as follows. Consider a network whose topology is completely unknown but whose nodes consist of two types: one accessible and another inaccessible from the outside world. The accessible nodes can be observed or monitored, and it is assumed that time series are available from each node in this group. The inaccessible nodes are shielded from the outside and they are essentially''hidden''. The question is, based solely on the available time series from the accessible nodes, can the existence and …