A general scheme to get insight and to control postcollision interaction (PCI) by means of sequential double ionization with two high-frequency pulses is discussed. In particular, we propose to consider PCI of a slow photoelectron released by the pump pulse from a neutral atom with a fast photoelectron released by the time-delayed probe pulse from the created ion. This scheme is exemplified by the ab initio calculations performed for the prototypical helium atom. In order to visualize PCI effects in real time and real space, the corresponding time-dependent Schrödinger equation is solved by propagating two-electron wave packets in terms of essential stationary eigenstates of the unperturbed Hamiltonian. It is demonstrated that the exchange of energy between the slow and fast photoelectron wave packets in continuum, as well as the recapture of threshold photoelectrons owing to the PCI, can be controlled by the properties of the ionizing pulses and the time delay between them.