  We present the first spectroscopic observations in the interval 0.8-4.0
microns, complemented with HST/UV and optical spectroscopy, of the narrow line
Seyfert 1 galaxy Mrk766. The NIR spectrum is characterized by permitted lines
of HI, HeI, HeII and FeII, and forbidden lines of [SII], [SIII] and [FeII]
among others. High ionized species such as [SiIX], [SiX], [SIX] and [MgVII] are
also observed. The continuum has a complex shape, with contribution of the
central engine, circumnuclear stellar population and dust. This last component
is evidenced by the presence of an excess of emission peaking at 2.25 microns,
fitted by blackbody function with T_bb=1200K. That temperature is close to the
evaporation temperature of graphite grains. As such, it provides strong
evidence of hot dust, probably very close to the nucleus. Consistent modeling
of the line and broad band continuum spectrum by composite models, which
account for the photoionizing flux of the central engine and shocks, shows that
the shock velocities are between 100 and 500 km/s, the preshock densities
between 100 and 1000 cm^-3 and the radiation fluxes from the active centre
between 10^9 and 5x10^12 photons cm^-2 s^-1 eV^-1 at 1 Ryd with spectral
indices $\alpha_{UV}$=-1.5 and $\alpha_X$=-0.4. Adopting silicon grains,
dust-to-gas ratios are between 10^-{6} and 4x10$^{-4}$ by mass. The emitting
clouds are at an average distance of 160 pc from the centre, with high velocity
clouds closer and low velocity clouds farther from the centre. The N/H relative
abundance could be twice solar. In constrast, Fe is depleted from the gaseous
phase by a factor >2. Ratios of calculated to observed line ratios to Hbeta
indicate an average contribution of the broad line region to the observed Hbeta
of about 40%.
