  Hypothetical particles with tiny electric charges (millicharged particles or
MCPs) can be produced in electron-positron annihilation if kinematically
allowed. Typical searches for them at $e^+e^-$ colliders exploit a signature of
a single photon with missing energy carried away by the undetected MCP pair. We
put forward an idea to look alternatively for MCP energy deposits inside a
tracker, which is a direct observation. The new signature is relevant for
non-relativistic MCPs, and we illustrate its power on the example of the
$c$-$\tau$ factory, where we argued that the corresponding searches may be
background-free. We find that it can probe the MCP charge down to
$3\times10^{-3}$ of the electron charge for the MCP masses in ${\cal O}(5)$ MeV
vicinity of each energy beam value where the factory will collect a luminosity
of 100 fb$^{-1}$ in one year. This mass region is unreachable with the searches
for missing energy and single photon.
