  We demonstrate sub-cycle control of frustrated double ionization (FDI) in the
two-electron triatomic molecule D$_3^+$ when driven by two orthogonally
polarized two-color laser fields. We employ a three-dimensional semi-classical
model that fully accounts for the electron and nuclear motion in strong fields.
We control FDI triggered by a strong near-infrared laser field with a weak
mid-infrared laser field. This control as a function of the time delay between
the two pulses is demonstrated when the FDI probability and the distribution of
the momentum of the escaping electron along the mid-infrared laser field are
considered in conjunction. We find that the momentum distribution of the
escaping electron has a hive-shape with features that can accurately be mapped
to the time one of the two electrons tunnel-ionizes at the start of the
break-up process. This mapping distinguishes consecutive tunnel-ionization
times within a cycle of the mid-infrared laser field.
