  We present a detailed investigation of the flaring activity observed from a
BL Lac object, S5 0716+714 , during its brightest ever optical state in the
second half of January 2015. Observed almost simultaneously in the optical,
X-rays and {\gamma}-rays, a significant change in the degree of optical
polarization (PD) and a swing in the position angle (PA) of polarization were
recorded. A detection in the TeV (VHE) was also reported by the MAGIC
consortium during this flaring episode. Two prominent sub-flares, peaking about
5-days apart, were seen in almost all the energy bands. The multi-wavelength
light-curves, spectral energy distribution (SED) and polarization are modeled
using the time-dependent code developed by Zhang et al. (2014). This model
assumes a straight jet threaded by large scale helical magnetic fields taking
into account the light travel time effects, incorporating synchrotron flux and
polarization in 3D geometry. The rapid variation in PD and rotation in PA are
most likely due to re-connections happening in the emission region in the jet,
as suggested by the change in the ratio of toroidal to poloidal components of
magnetic field during quiescent and flaring states.
