  We propose a holographic model for local quench in 1+1 dimensional Conformal
Field Theory (CFT). The local quench is produced by joining two identical CFT's
on semi-infinite lines. When these theories have a zero boundary entropy, we
use the AdS/Boundary CFT proposal to describe this process in terms of bulk
physics. Boundaries of the original CFT's are extended in AdS as dynamical
surfaces. In our holographic picture these surfaces detach from the boundary
and form a closed folded string which can propagate in the bulk. The dynamics
of this string is governed by the tensionless Yo-Yo string solution and its
subsequent evolution determines the time dependence after quench. We use this
model to calculate holographic Entanglement Entropy (EE) of an interval as a
function of time. We propose how the falling string deforms Ryu-Takayanagi's
curves. Using the deformed curves we calculate EE and find complete agreement
with field theory results.
