The invention refers to an auto-injector (1) comprising an elongate housing (2), a syringe (5) with a hollow injection needle (6) and a stopper (13), wherein the syringe (5) is arranged in a syringe carrier (4) slidably with respect to the housing (2),- a single compression spring (7) capable of, upon activation:- pushing the needle (6) from a covered position inside the housing (2) into an advanced position through the orifice and past the proximal end (P) for insertion into an injection site,- operating the syringe (5) to inject the dose of medicament (M), and- retracting the syringe (5) with the needle (6) into the covered position after at least partiallydelivering the medicament (M),- activating means (3) arranged to lock the spring means (7) in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the compression spring (7) for injection.A thrust tube (8) is arranged to transmit load from the compression spring (7) via a plunger (9) to the syringe (5) and/or the stopper (13), wherein the thrust tube (8) is arranged to be rotationally constrained relative to the housing (2), wherein the thrust tube (8) and the plunger (9) exhibit corresponding first and second threads (9.3, 8.2) having a first direction arranged to be engaged at least in an initial state. The plunger (9) is arranged to be rotationally released upon removal of the auto-injector (1) from the injection site resulting in rotation of the plunger (9) and consequently disengagement of the corresponding first and second threads (9.3, 8.2). The thrust tube (8) translates further and engages a corresponding third thread (12.1) of a retract collar (12) which is engaged to the syringe carrier (4) by corresponding fourth and fifth threads (12.2, 4.1) having the opposite direction of the first direction so that continued translation of the thrust tube (8) in proximal direction (P) results in rotation of the retract collar (12) and translation of the syringe carrier (4
